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	$230.73	4.584%	$241.3067	$241.31	$241.30	$241.30
Purchase #2	$160.69	4.104%	$167.2847	$167.28	$167.30	$167.30
Purchase #3	$37.49	6.593%	$39.9617	$39.96	$39.95	$40.00
Purchase #4	$223.83	13.379%	$253.7762	$253.78	$253.80	$253.80
Purchase #5	$82.51	11.788%	$92.2363	$92.24	$92.25	$92.20
Purchase #6	$209.99	10.426%	$231.8836	$231.88	$231.90	$231.90
Purchase #7	$57.53	8.346%	$62.3315	$62.33	$62.35	$62.30
7 purchase totals =	$1,002.77		$1,088.7807	$1,088.78	$1,088.85	$1,088.80