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	$243.86	13.869%	$277.6809	$277.68	$277.70	$277.70
Purchase #2	$174.43	4.430%	$182.1572	$182.16	$182.15	$182.20
Purchase #3	$28.53	13.449%	$32.367	$32.37	$32.35	$32.40
Purchase #4	$202.35	6.429%	$215.3591	$215.36	$215.35	$215.40
Purchase #5	$40.45	3.148%	$41.7234	$41.72	$41.70	$41.70
Purchase #6	$124.63	9.818%	$136.8662	$136.87	$136.85	$136.90
Purchase #7	$165.60	13.240%	$187.5254	$187.53	$187.55	$187.50
7 purchase totals =	$979.85		$1,073.6792	$1,073.69	$1,073.65	$1,073.80