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	$143.38	13.295%	$162.4424	$162.44	$162.45	$162.40
Purchase #2	$146.58	13.247%	$165.9975	$166.00	$166.00	$166.00
Purchase #3	$213.56	7.374%	$229.3079	$229.31	$229.30	$229.30
Purchase #4	$111.50	11.453%	$124.2701	$124.27	$124.25	$124.30
Purchase #5	$188.96	3.710%	$195.9704	$195.97	$195.95	$196.00
Purchase #6	$170.72	5.274%	$179.7238	$179.72	$179.70	$179.70
Purchase #7	$136.68	11.579%	$152.5062	$152.51	$152.50	$152.50
7 purchase totals =	$1,111.38		$1,210.2183	$1,210.22	$1,210.15	$1,210.20