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	$164.30	9.148%	$179.3302	$179.33	$179.35	$179.30
Purchase #2	$62.53	4.410%	$65.2876	$65.29	$65.30	$65.30
Purchase #3	$104.48	6.216%	$110.9745	$110.97	$110.95	$111.00
Purchase #4	$98.95	10.532%	$109.3714	$109.37	$109.35	$109.40
Purchase #5	$136.72	11.268%	$152.1256	$152.13	$152.15	$152.10
Purchase #6	$7.65	3.148%	$7.8908	$7.89	$7.90	$7.90
Purchase #7	$176.27	9.136%	$192.374	$192.37	$192.35	$192.40
7 purchase totals =	$750.90		$817.3541	$817.35	$817.35	$817.40