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	$149.57	6.645%	$159.5089	$159.51	$159.50	$159.50
Purchase #2	$139.83	5.198%	$147.0984	$147.10	$147.10	$147.10
Purchase #3	$43.72	8.150%	$47.2832	$47.28	$47.30	$47.30
Purchase #4	$46.59	7.301%	$49.9915	$49.99	$50.00	$50.00
Purchase #5	$175.69	7.763%	$189.3288	$189.33	$189.35	$189.30
Purchase #6	$13.47	3.244%	$13.907	$13.91	$13.90	$13.90
Purchase #7	$18.91	7.843%	$20.3931	$20.39	$20.40	$20.40
7 purchase totals =	$587.78		$627.5109	$627.51	$627.55	$627.50