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	$202.64	8.518%	$219.9009	$219.90	$219.90	$219.90
Purchase #2	$12.52	4.654%	$13.1027	$13.10	$13.10	$13.10
Purchase #3	$33.88	7.414%	$36.3919	$36.39	$36.40	$36.40
Purchase #4	$209.73	10.338%	$231.4119	$231.41	$231.40	$231.40
Purchase #5	$88.55	12.872%	$99.9482	$99.95	$99.95	$99.90
Purchase #6	$141.39	5.321%	$148.9134	$148.91	$148.90	$148.90
Purchase #7	$218.91	6.808%	$233.8134	$233.81	$233.80	$233.80
7 purchase totals =	$907.62		$983.4824	$983.47	$983.45	$983.40