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	$167.93	10.827%	$186.1118	$186.11	$186.10	$186.10
Purchase #2	$10.78	7.176%	$11.5536	$11.55	$11.55	$11.60
Purchase #3	$115.94	13.388%	$131.462	$131.46	$131.45	$131.50
Purchase #4	$160.38	3.365%	$165.7768	$165.78	$165.80	$165.80
Purchase #5	$17.34	11.561%	$19.3447	$19.34	$19.35	$19.30
Purchase #6	$110.61	12.829%	$124.8002	$124.80	$124.80	$124.80
Purchase #7	$139.81	13.354%	$158.4802	$158.48	$158.50	$158.50
7 purchase totals =	$722.79		$797.5293	$797.52	$797.55	$797.60