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	$207.38	11.467%	$231.1603	$231.16	$231.15	$231.20
Purchase #2	$52.69	12.240%	$59.1393	$59.14	$59.15	$59.10
Purchase #3	$73.74	11.783%	$82.4288	$82.43	$82.45	$82.40
Purchase #4	$55.66	12.835%	$62.804	$62.80	$62.80	$62.80
Purchase #5	$169.44	3.638%	$175.6042	$175.60	$175.60	$175.60
Purchase #6	$208.28	7.502%	$223.9052	$223.91	$223.90	$223.90
Purchase #7	$143.64	9.522%	$157.3174	$157.32	$157.30	$157.30
7 purchase totals =	$910.83		$992.3592	$992.36	$992.35	$992.30