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	$119.28	9.762%	$130.9241	$130.92	$130.90	$130.90
Purchase #2	$189.94	10.502%	$209.8875	$209.89	$209.90	$209.90
Purchase #3	$210.84	12.369%	$236.9188	$236.92	$236.90	$236.90
Purchase #4	$133.29	13.287%	$151.0002	$151.00	$151.00	$151.00
Purchase #5	$172.42	9.520%	$188.8344	$188.83	$188.85	$188.80
Purchase #6	$90.27	5.708%	$95.4226	$95.42	$95.40	$95.40
Purchase #7	$174.56	12.703%	$196.7344	$196.73	$196.75	$196.70
7 purchase totals =	$1,090.60		$1,209.7220	$1,209.71	$1,209.70	$1,209.60