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	$208.25	8.755%	$226.4823	$226.48	$226.50	$226.50
Purchase #2	$162.42	13.456%	$184.2752	$184.28	$184.30	$184.30
Purchase #3	$48.51	12.680%	$54.6611	$54.66	$54.65	$54.70
Purchase #4	$139.84	8.266%	$151.3992	$151.40	$151.40	$151.40
Purchase #5	$52.25	7.274%	$56.0507	$56.05	$56.05	$56.10
Purchase #6	$110.33	6.629%	$117.6438	$117.64	$117.65	$117.60
Purchase #7	$99.74	10.228%	$109.9414	$109.94	$109.95	$109.90
7 purchase totals =	$821.34		$900.4537	$900.45	$900.50	$900.50