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	$108.55	13.866%	$123.6015	$123.60	$123.60	$123.60
Purchase #2	$188.48	8.267%	$204.0616	$204.06	$204.05	$204.10
Purchase #3	$53.62	3.190%	$55.3305	$55.33	$55.35	$55.30
Purchase #4	$135.41	12.827%	$152.779	$152.78	$152.80	$152.80
Purchase #5	$170.55	11.363%	$189.9296	$189.93	$189.95	$189.90
Purchase #6	$132.44	3.119%	$136.5708	$136.57	$136.55	$136.60
Purchase #7	$179.88	4.605%	$188.1635	$188.16	$188.15	$188.20
7 purchase totals =	$968.93		$1,050.4365	$1,050.43	$1,050.45	$1,050.50