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	$216.97	13.527%	$246.3195	$246.32	$246.30	$246.30
Purchase #2	$166.81	3.472%	$172.6016	$172.60	$172.60	$172.60
Purchase #3	$175.51	11.755%	$196.1412	$196.14	$196.15	$196.10
Purchase #4	$145.64	5.337%	$153.4128	$153.41	$153.40	$153.40
Purchase #5	$124.91	4.123%	$130.06	$130.06	$130.05	$130.10
Purchase #6	$167.59	7.402%	$179.995	$180.00	$180.00	$180.00
Purchase #7	$137.41	7.556%	$147.7927	$147.79	$147.80	$147.80
7 purchase totals =	$1,134.84		$1,226.3228	$1,226.32	$1,226.30	$1,226.30