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	$147.36	12.182%	$165.3114	$165.31	$165.30	$165.30
Purchase #2	$94.95	11.263%	$105.6442	$105.64	$105.65	$105.60
Purchase #3	$240.93	9.810%	$264.5652	$264.57	$264.55	$264.60
Purchase #4	$59.48	7.748%	$64.0885	$64.09	$64.10	$64.10
Purchase #5	$140.65	8.538%	$152.6587	$152.66	$152.65	$152.70
Purchase #6	$39.57	4.659%	$41.4136	$41.41	$41.40	$41.40
Purchase #7	$198.91	12.280%	$223.3361	$223.34	$223.35	$223.30
7 purchase totals =	$921.85		$1,017.0177	$1,017.02	$1,017.00	$1,017.00