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	$81.51	9.241%	$89.0423	$89.04	$89.05	$89.00
Purchase #2	$31.95	5.474%	$33.6989	$33.70	$33.70	$33.70
Purchase #3	$40.27	13.154%	$45.5671	$45.57	$45.55	$45.60
Purchase #4	$65.38	9.195%	$71.3917	$71.39	$71.40	$71.40
Purchase #5	$60.47	11.843%	$67.6315	$67.63	$67.65	$67.60
Purchase #6	$10.61	12.315%	$11.9166	$11.92	$11.90	$11.90
Purchase #7	$98.56	10.574%	$108.9817	$108.98	$109.00	$109.00
7 purchase totals =	$388.75		$428.2298	$428.23	$428.25	$428.20