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	$90.49	11.819%	$101.185	$101.19	$101.20	$101.20
Purchase #2	$101.76	4.223%	$106.0573	$106.06	$106.05	$106.10
Purchase #3	$172.80	11.741%	$193.0884	$193.09	$193.10	$193.10
Purchase #4	$38.94	3.534%	$40.3161	$40.32	$40.30	$40.30
Purchase #5	$103.45	7.529%	$111.2388	$111.24	$111.25	$111.20
Purchase #6	$71.86	10.449%	$79.3687	$79.37	$79.35	$79.40
Purchase #7	$78.27	4.157%	$81.5237	$81.52	$81.50	$81.50
7 purchase totals =	$657.57		$712.7780	$712.79	$712.75	$712.80