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	$167.33	12.397%	$188.0739	$188.07	$188.05	$188.10
Purchase #2	$68.33	3.263%	$70.5596	$70.56	$70.55	$70.60
Purchase #3	$110.83	11.239%	$123.2862	$123.29	$123.30	$123.30
Purchase #4	$244.88	10.237%	$269.9484	$269.95	$269.95	$269.90
Purchase #5	$40.62	11.362%	$45.2352	$45.24	$45.25	$45.20
Purchase #6	$110.28	6.808%	$117.7879	$117.79	$117.80	$117.80
Purchase #7	$220.42	13.817%	$250.8754	$250.88	$250.90	$250.90
7 purchase totals =	$962.69		$1,065.7666	$1,065.78	$1,065.80	$1,065.80