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	$233.80	13.115%	$264.4629	$264.46	$264.45	$264.50
Purchase #2	$173.38	5.245%	$182.4738	$182.47	$182.45	$182.50
Purchase #3	$12.76	10.609%	$14.1137	$14.11	$14.10	$14.10
Purchase #4	$236.73	7.231%	$253.8479	$253.85	$253.85	$253.80
Purchase #5	$159.59	3.155%	$164.6251	$164.63	$164.65	$164.60
Purchase #6	$77.76	3.370%	$80.3805	$80.38	$80.40	$80.40
Purchase #7	$91.83	9.815%	$100.8431	$100.84	$100.85	$100.80
7 purchase totals =	$985.85		$1,060.7470	$1,060.74	$1,060.75	$1,060.70