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	$80.76	6.143%	$85.7211	$85.72	$85.70	$85.70
Purchase #2	$166.64	3.663%	$172.744	$172.74	$172.75	$172.70
Purchase #3	$56.90	13.142%	$64.3778	$64.38	$64.40	$64.40
Purchase #4	$214.52	3.632%	$222.3114	$222.31	$222.30	$222.30
Purchase #5	$162.28	3.433%	$167.8511	$167.85	$167.85	$167.90
Purchase #6	$206.61	6.454%	$219.9446	$219.94	$219.95	$219.90
Purchase #7	$36.86	5.149%	$38.7579	$38.76	$38.75	$38.80
7 purchase totals =	$924.57		$971.7079	$971.70	$971.70	$971.70