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	$61.44	9.355%	$67.1877	$67.19	$67.20	$67.20
Purchase #2	$152.62	4.278%	$159.1491	$159.15	$159.15	$159.10
Purchase #3	$24.29	3.275%	$25.0855	$25.09	$25.10	$25.10
Purchase #4	$94.93	4.348%	$99.0576	$99.06	$99.05	$99.10
Purchase #5	$114.33	7.731%	$123.1689	$123.17	$123.15	$123.20
Purchase #6	$77.89	12.713%	$87.7922	$87.79	$87.80	$87.80
Purchase #7	$30.28	4.729%	$31.7119	$31.71	$31.70	$31.70
7 purchase totals =	$555.78		$593.1529	$593.16	$593.15	$593.20