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	$141.74	6.636%	$151.1459	$151.15	$151.15	$151.10
Purchase #2	$242.50	8.571%	$263.2847	$263.28	$263.30	$263.30
Purchase #3	$72.51	9.439%	$79.3542	$79.35	$79.35	$79.40
Purchase #4	$64.59	12.258%	$72.5074	$72.51	$72.50	$72.50
Purchase #5	$247.48	4.751%	$259.2378	$259.24	$259.25	$259.20
Purchase #6	$37.91	12.641%	$42.7022	$42.70	$42.70	$42.70
Purchase #7	$217.97	9.322%	$238.2892	$238.29	$238.30	$238.30
7 purchase totals =	$1,024.70		$1,106.5214	$1,106.52	$1,106.55	$1,106.50