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	$235.36	6.619%	$250.9385	$250.94	$250.95	$250.90
Purchase #2	$209.63	5.741%	$221.6649	$221.66	$221.65	$221.70
Purchase #3	$18.75	7.357%	$20.1294	$20.13	$20.15	$20.10
Purchase #4	$147.38	6.584%	$157.0835	$157.08	$157.10	$157.10
Purchase #5	$68.88	11.611%	$76.8777	$76.88	$76.90	$76.90
Purchase #6	$81.27	10.255%	$89.6042	$89.60	$89.60	$89.60
Purchase #7	$65.40	3.860%	$67.9244	$67.92	$67.90	$67.90
7 purchase totals =	$826.67		$884.2226	$884.21	$884.25	$884.20