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	$100.75	3.557%	$104.3337	$104.33	$104.35	$104.30
Purchase #2	$242.54	9.519%	$265.6274	$265.63	$265.65	$265.60
Purchase #3	$209.50	8.711%	$227.7495	$227.75	$227.75	$227.70
Purchase #4	$165.99	12.115%	$186.0997	$186.10	$186.10	$186.10
Purchase #5	$136.67	3.570%	$141.5491	$141.55	$141.55	$141.50
Purchase #6	$137.38	8.108%	$148.5188	$148.52	$148.50	$148.50
Purchase #7	$101.60	9.799%	$111.5558	$111.56	$111.55	$111.60
7 purchase totals =	$1,094.43		$1,185.4340	$1,185.44	$1,185.45	$1,185.30