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	$103.43	13.145%	$117.0259	$117.03	$117.05	$117.00
Purchase #2	$227.67	10.227%	$250.9538	$250.95	$250.95	$251.00
Purchase #3	$79.73	13.280%	$90.3181	$90.32	$90.30	$90.30
Purchase #4	$151.80	10.398%	$167.5842	$167.58	$167.60	$167.60
Purchase #5	$191.87	4.738%	$200.9608	$200.96	$200.95	$201.00
Purchase #6	$209.52	6.360%	$222.8455	$222.85	$222.85	$222.80
Purchase #7	$235.71	7.503%	$253.3953	$253.40	$253.40	$253.40
7 purchase totals =	$1,199.73		$1,303.0836	$1,303.09	$1,303.10	$1,303.10