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	$222.34	9.367%	$243.1666	$243.17	$243.15	$243.20
Purchase #2	$155.55	13.267%	$176.1868	$176.19	$176.20	$176.20
Purchase #3	$63.35	9.722%	$69.5089	$69.51	$69.50	$69.50
Purchase #4	$105.89	5.274%	$111.4746	$111.47	$111.45	$111.50
Purchase #5	$114.42	9.703%	$125.5222	$125.52	$125.50	$125.50
Purchase #6	$203.42	9.279%	$222.2953	$222.30	$222.30	$222.30
Purchase #7	$110.88	11.661%	$123.8097	$123.81	$123.80	$123.80
7 purchase totals =	$975.85		$1,071.9641	$1,071.97	$1,071.90	$1,072.00