Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.39	10.262%	$168.0283	$168.03	$168.05	$168.00
Purchase #2	$96.91	8.821%	$105.4584	$105.46	$105.45	$105.50
Purchase #3	$140.67	9.231%	$153.6552	$153.66	$153.65	$153.70
Purchase #4	$212.38	10.289%	$234.2318	$234.23	$234.25	$234.20
Purchase #5	$126.94	12.618%	$142.9573	$142.96	$142.95	$143.00
Purchase #6	$242.69	4.375%	$253.3077	$253.31	$253.30	$253.30
Purchase #7	$104.36	9.836%	$114.6248	$114.62	$114.60	$114.60
7 purchase totals =	$1,076.34		$1,172.2635	$1,172.27	$1,172.25	$1,172.30