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	$183.82	11.407%	$204.7883	$204.79	$204.80	$204.80
Purchase #2	$143.58	11.384%	$159.9251	$159.93	$159.95	$159.90
Purchase #3	$126.85	12.304%	$142.4576	$142.46	$142.45	$142.50
Purchase #4	$38.25	5.140%	$40.2161	$40.22	$40.20	$40.20
Purchase #5	$174.28	5.276%	$183.475	$183.48	$183.50	$183.50
Purchase #6	$144.45	12.534%	$162.5554	$162.56	$162.55	$162.60
Purchase #7	$245.37	3.393%	$253.6954	$253.70	$253.70	$253.70
7 purchase totals =	$1,056.60		$1,147.1129	$1,147.14	$1,147.15	$1,147.20