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	$67.86	7.294%	$72.8097	$72.81	$72.80	$72.80
Purchase #2	$127.25	12.740%	$143.4617	$143.46	$143.45	$143.50
Purchase #3	$149.67	5.767%	$158.3015	$158.30	$158.30	$158.30
Purchase #4	$217.53	13.288%	$246.4354	$246.44	$246.45	$246.40
Purchase #5	$172.57	10.102%	$190.003	$190.00	$190.00	$190.00
Purchase #6	$176.87	4.743%	$185.2589	$185.26	$185.25	$185.30
Purchase #7	$216.57	11.241%	$240.9146	$240.91	$240.90	$240.90
7 purchase totals =	$1,128.32		$1,237.1848	$1,237.18	$1,237.15	$1,237.20