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	$232.64	7.553%	$250.2113	$250.21	$250.20	$250.20
Purchase #2	$211.95	10.391%	$233.9737	$233.97	$233.95	$234.00
Purchase #3	$36.52	9.674%	$40.0529	$40.05	$40.05	$40.10
Purchase #4	$35.51	13.555%	$40.3234	$40.32	$40.30	$40.30
Purchase #5	$62.82	8.130%	$67.9273	$67.93	$67.95	$67.90
Purchase #6	$91.50	10.169%	$100.8046	$100.80	$100.80	$100.80
Purchase #7	$95.28	4.432%	$99.5028	$99.50	$99.50	$99.50
7 purchase totals =	$766.22		$832.7960	$832.78	$832.75	$832.80