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	$168.96	12.480%	$190.0462	$190.05	$190.05	$190.00
Purchase #2	$62.47	8.772%	$67.9499	$67.95	$67.95	$67.90
Purchase #3	$231.33	11.853%	$258.7495	$258.75	$258.75	$258.70
Purchase #4	$226.72	6.855%	$242.2617	$242.26	$242.25	$242.30
Purchase #5	$81.60	10.191%	$89.9159	$89.92	$89.90	$89.90
Purchase #6	$117.33	8.490%	$127.2913	$127.29	$127.30	$127.30
Purchase #7	$6.74	3.214%	$6.9566	$6.96	$6.95	$7.00
7 purchase totals =	$895.15		$983.1711	$983.18	$983.15	$983.10