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	$154.35	11.213%	$171.6573	$171.66	$171.65	$171.70
Purchase #2	$181.79	10.312%	$200.5362	$200.54	$200.55	$200.50
Purchase #3	$247.71	3.466%	$256.2956	$256.30	$256.30	$256.30
Purchase #4	$165.32	11.646%	$184.5732	$184.57	$184.55	$184.60
Purchase #5	$150.36	13.773%	$171.0691	$171.07	$171.05	$171.10
Purchase #6	$44.33	4.442%	$46.2991	$46.30	$46.30	$46.30
Purchase #7	$138.47	9.508%	$151.6357	$151.64	$151.65	$151.60
7 purchase totals =	$1,082.33		$1,182.0662	$1,182.08	$1,182.05	$1,182.10