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	$208.92	11.873%	$233.7251	$233.73	$233.75	$233.70
Purchase #2	$82.68	4.424%	$86.3378	$86.34	$86.35	$86.30
Purchase #3	$53.56	10.843%	$59.3675	$59.37	$59.35	$59.40
Purchase #4	$93.91	3.582%	$97.2739	$97.27	$97.25	$97.30
Purchase #5	$22.49	8.303%	$24.3573	$24.36	$24.35	$24.40
Purchase #6	$99.70	3.644%	$103.3331	$103.33	$103.35	$103.30
Purchase #7	$54.54	8.411%	$59.1274	$59.13	$59.15	$59.10
7 purchase totals =	$615.80		$663.5221	$663.53	$663.55	$663.50