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	$189.43	9.114%	$206.6947	$206.69	$206.70	$206.70
Purchase #2	$193.25	6.198%	$205.2276	$205.23	$205.25	$205.20
Purchase #3	$33.25	11.280%	$37.0006	$37.00	$37.00	$37.00
Purchase #4	$157.40	5.123%	$165.4636	$165.46	$165.45	$165.50
Purchase #5	$219.50	4.597%	$229.5904	$229.59	$229.60	$229.60
Purchase #6	$21.60	13.126%	$24.4352	$24.44	$24.45	$24.40
Purchase #7	$201.91	7.402%	$216.8554	$216.86	$216.85	$216.90
7 purchase totals =	$1,016.34		$1,085.2675	$1,085.27	$1,085.30	$1,085.30