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	$46.71	11.593%	$52.1251	$52.13	$52.15	$52.10
Purchase #2	$67.43	6.765%	$71.9916	$71.99	$72.00	$72.00
Purchase #3	$52.38	8.727%	$56.9512	$56.95	$56.95	$57.00
Purchase #4	$18.75	7.424%	$20.142	$20.14	$20.15	$20.10
Purchase #5	$26.42	3.614%	$27.3748	$27.37	$27.35	$27.40
Purchase #6	$159.48	7.735%	$171.8158	$171.82	$171.80	$171.80
Purchase #7	$144.91	6.595%	$154.4668	$154.47	$154.45	$154.50
7 purchase totals =	$516.08		$554.8673	$554.87	$554.85	$554.90