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	$97.51	3.287%	$100.7152	$100.72	$100.70	$100.70
Purchase #2	$92.58	13.760%	$105.319	$105.32	$105.30	$105.30
Purchase #3	$67.32	5.573%	$71.0717	$71.07	$71.05	$71.10
Purchase #4	$105.25	13.843%	$119.8198	$119.82	$119.80	$119.80
Purchase #5	$66.36	13.106%	$75.0571	$75.06	$75.05	$75.10
Purchase #6	$161.78	4.768%	$169.4937	$169.49	$169.50	$169.50
Purchase #7	$101.71	9.370%	$111.2402	$111.24	$111.25	$111.20
7 purchase totals =	$692.51		$752.7167	$752.72	$752.65	$752.70