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	$227.43	9.449%	$248.9199	$248.92	$248.90	$248.90
Purchase #2	$186.64	13.681%	$212.1742	$212.17	$212.15	$212.20
Purchase #3	$98.85	13.452%	$112.1473	$112.15	$112.15	$112.10
Purchase #4	$8.91	13.769%	$10.1368	$10.14	$10.15	$10.10
Purchase #5	$154.30	13.114%	$174.5349	$174.53	$174.55	$174.50
Purchase #6	$111.31	10.767%	$123.2947	$123.29	$123.30	$123.30
Purchase #7	$57.84	11.506%	$64.4951	$64.50	$64.50	$64.50
7 purchase totals =	$845.28		$945.7029	$945.70	$945.70	$945.60