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	$238.76	7.478%	$256.6145	$256.61	$256.60	$256.60
Purchase #2	$147.77	5.221%	$155.4851	$155.49	$155.50	$155.50
Purchase #3	$97.33	12.858%	$109.8447	$109.84	$109.85	$109.80
Purchase #4	$115.62	9.382%	$126.4675	$126.47	$126.45	$126.50
Purchase #5	$31.95	11.261%	$35.5479	$35.55	$35.55	$35.50
Purchase #6	$101.37	10.220%	$111.73	$111.73	$111.75	$111.70
Purchase #7	$231.38	9.825%	$254.1131	$254.11	$254.10	$254.10
7 purchase totals =	$964.18		$1,049.8028	$1,049.80	$1,049.80	$1,049.70