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	$77.61	7.341%	$83.3074	$83.31	$83.30	$83.30
Purchase #2	$6.88	7.335%	$7.3846	$7.38	$7.40	$7.40
Purchase #3	$196.43	4.136%	$204.5543	$204.55	$204.55	$204.60
Purchase #4	$115.49	13.680%	$131.289	$131.29	$131.30	$131.30
Purchase #5	$223.73	13.641%	$254.249	$254.25	$254.25	$254.20
Purchase #6	$151.78	9.154%	$165.6739	$165.67	$165.65	$165.70
Purchase #7	$104.28	9.478%	$114.1637	$114.16	$114.15	$114.20
7 purchase totals =	$876.20		$960.6219	$960.61	$960.60	$960.70