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	$106.76	4.641%	$111.7147	$111.71	$111.70	$111.70
Purchase #2	$110.58	9.340%	$120.9082	$120.91	$120.90	$120.90
Purchase #3	$100.59	3.213%	$103.822	$103.82	$103.80	$103.80
Purchase #4	$141.59	4.502%	$147.9644	$147.96	$147.95	$148.00
Purchase #5	$5.90	10.207%	$6.5022	$6.50	$6.50	$6.50
Purchase #6	$104.30	6.336%	$110.9084	$110.91	$110.90	$110.90
Purchase #7	$122.51	4.105%	$127.539	$127.54	$127.55	$127.50
7 purchase totals =	$692.23		$729.3589	$729.35	$729.30	$729.30