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	$169.49	10.602%	$187.4593	$187.46	$187.45	$187.50
Purchase #2	$87.33	12.148%	$97.9388	$97.94	$97.95	$97.90
Purchase #3	$217.74	10.371%	$240.3218	$240.32	$240.30	$240.30
Purchase #4	$74.59	9.217%	$81.465	$81.47	$81.45	$81.50
Purchase #5	$149.47	7.678%	$160.9463	$160.95	$160.95	$160.90
Purchase #6	$165.33	4.225%	$172.3152	$172.32	$172.30	$172.30
Purchase #7	$240.92	11.745%	$269.2161	$269.22	$269.20	$269.20
7 purchase totals =	$1,104.87		$1,209.6625	$1,209.68	$1,209.60	$1,209.60