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	$199.38	5.552%	$210.4496	$210.45	$210.45	$210.40
Purchase #2	$130.50	13.813%	$148.526	$148.53	$148.55	$148.50
Purchase #3	$243.80	7.281%	$261.5511	$261.55	$261.55	$261.60
Purchase #4	$183.42	7.176%	$196.5822	$196.58	$196.60	$196.60
Purchase #5	$91.28	13.870%	$103.9405	$103.94	$103.95	$103.90
Purchase #6	$16.67	9.665%	$18.2812	$18.28	$18.30	$18.30
Purchase #7	$153.70	13.428%	$174.3388	$174.34	$174.35	$174.30
7 purchase totals =	$1,018.75		$1,113.6694	$1,113.67	$1,113.75	$1,113.60