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	$146.48	13.127%	$165.7084	$165.71	$165.70	$165.70
Purchase #2	$64.63	4.820%	$67.7452	$67.75	$67.75	$67.70
Purchase #3	$215.98	12.821%	$243.6708	$243.67	$243.65	$243.70
Purchase #4	$142.78	9.304%	$156.0643	$156.06	$156.05	$156.10
Purchase #5	$83.43	3.805%	$86.6045	$86.60	$86.60	$86.60
Purchase #6	$219.84	3.487%	$227.5058	$227.51	$227.50	$227.50
Purchase #7	$72.33	9.778%	$79.4024	$79.40	$79.40	$79.40
7 purchase totals =	$945.47		$1,026.7014	$1,026.70	$1,026.65	$1,026.70