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	$72.93	11.537%	$81.3439	$81.34	$81.35	$81.30
Purchase #2	$186.82	5.154%	$196.4487	$196.45	$196.45	$196.40
Purchase #3	$118.65	4.612%	$124.1221	$124.12	$124.10	$124.10
Purchase #4	$245.53	11.399%	$273.518	$273.52	$273.50	$273.50
Purchase #5	$45.83	5.304%	$48.2608	$48.26	$48.25	$48.30
Purchase #6	$96.75	12.800%	$109.134	$109.13	$109.15	$109.10
Purchase #7	$128.57	6.672%	$137.1482	$137.15	$137.15	$137.10
7 purchase totals =	$895.08		$969.9757	$969.97	$969.95	$969.80