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	$68.92	3.810%	$71.5459	$71.55	$71.55	$71.50
Purchase #2	$82.99	10.841%	$91.9869	$91.99	$92.00	$92.00
Purchase #3	$114.76	11.519%	$127.9792	$127.98	$128.00	$128.00
Purchase #4	$200.90	3.741%	$208.4157	$208.42	$208.40	$208.40
Purchase #5	$100.41	10.436%	$110.8888	$110.89	$110.90	$110.90
Purchase #6	$109.75	7.808%	$118.3193	$118.32	$118.30	$118.30
Purchase #7	$219.71	11.317%	$244.5746	$244.57	$244.55	$244.60
7 purchase totals =	$897.44		$973.7104	$973.72	$973.70	$973.70