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	$98.28	10.596%	$108.6937	$108.69	$108.70	$108.70
Purchase #2	$13.99	4.758%	$14.6556	$14.66	$14.65	$14.70
Purchase #3	$101.54	10.221%	$111.9184	$111.92	$111.90	$111.90
Purchase #4	$95.39	11.127%	$106.004	$106.00	$106.00	$106.00
Purchase #5	$24.72	13.112%	$27.9613	$27.96	$27.95	$28.00
Purchase #6	$152.33	8.712%	$165.601	$165.60	$165.60	$165.60
Purchase #7	$198.42	3.634%	$205.6306	$205.63	$205.65	$205.60
7 purchase totals =	$684.67		$740.4646	$740.46	$740.45	$740.50