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	$219.61	11.613%	$245.1133	$245.11	$245.10	$245.10
Purchase #2	$62.30	12.725%	$70.2277	$70.23	$70.25	$70.20
Purchase #3	$98.46	10.842%	$109.135	$109.14	$109.15	$109.10
Purchase #4	$80.62	3.415%	$83.3732	$83.37	$83.35	$83.40
Purchase #5	$154.89	8.750%	$168.4429	$168.44	$168.45	$168.40
Purchase #6	$32.63	5.274%	$34.3509	$34.35	$34.35	$34.40
Purchase #7	$90.50	3.737%	$93.882	$93.88	$93.90	$93.90
7 purchase totals =	$739.01		$804.5250	$804.52	$804.55	$804.50