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	$174.67	12.373%	$196.2819	$196.28	$196.30	$196.30
Purchase #2	$11.91	8.521%	$12.9249	$12.92	$12.90	$12.90
Purchase #3	$21.43	6.334%	$22.7874	$22.79	$22.80	$22.80
Purchase #4	$105.49	10.388%	$116.4483	$116.45	$116.45	$116.40
Purchase #5	$172.69	8.589%	$187.5223	$187.52	$187.50	$187.50
Purchase #6	$180.65	3.131%	$186.3062	$186.31	$186.30	$186.30
Purchase #7	$227.60	4.760%	$238.4338	$238.43	$238.45	$238.40
7 purchase totals =	$894.44		$960.7048	$960.70	$960.70	$960.60