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	$79.61	3.358%	$82.2833	$82.28	$82.30	$82.30
Purchase #2	$216.34	12.416%	$243.2008	$243.20	$243.20	$243.20
Purchase #3	$164.30	9.791%	$180.3866	$180.39	$180.40	$180.40
Purchase #4	$245.95	6.570%	$262.1089	$262.11	$262.10	$262.10
Purchase #5	$143.70	9.473%	$157.3127	$157.31	$157.30	$157.30
Purchase #6	$71.65	9.526%	$78.4754	$78.48	$78.50	$78.50
Purchase #7	$134.98	11.401%	$150.3691	$150.37	$150.35	$150.40
7 purchase totals =	$1,056.53		$1,154.1368	$1,154.14	$1,154.15	$1,154.20