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	$147.27	7.739%	$158.6672	$158.67	$158.65	$158.70
Purchase #2	$81.41	5.456%	$85.8517	$85.85	$85.85	$85.90
Purchase #3	$101.74	3.767%	$105.5725	$105.57	$105.55	$105.60
Purchase #4	$208.58	6.703%	$222.5611	$222.56	$222.55	$222.60
Purchase #5	$89.59	5.759%	$94.7495	$94.75	$94.75	$94.70
Purchase #6	$54.95	11.604%	$61.3264	$61.33	$61.35	$61.30
Purchase #7	$225.31	4.278%	$234.9488	$234.95	$234.95	$234.90
7 purchase totals =	$908.85		$963.6772	$963.68	$963.65	$963.70