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	$122.46	6.341%	$130.2252	$130.23	$130.25	$130.20
Purchase #2	$25.52	10.380%	$28.169	$28.17	$28.15	$28.20
Purchase #3	$228.72	10.676%	$253.1381	$253.14	$253.15	$253.10
Purchase #4	$95.96	5.184%	$100.9346	$100.93	$100.95	$100.90
Purchase #5	$107.28	4.385%	$111.9842	$111.98	$112.00	$112.00
Purchase #6	$174.65	9.507%	$191.254	$191.25	$191.25	$191.30
Purchase #7	$239.62	4.130%	$249.5163	$249.52	$249.50	$249.50
7 purchase totals =	$994.21		$1,065.2214	$1,065.22	$1,065.25	$1,065.20