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	$245.28	3.532%	$253.9433	$253.94	$253.95	$253.90
Purchase #2	$85.28	6.672%	$90.9699	$90.97	$90.95	$91.00
Purchase #3	$225.89	8.707%	$245.5582	$245.56	$245.55	$245.60
Purchase #4	$141.55	12.603%	$159.3895	$159.39	$159.40	$159.40
Purchase #5	$60.66	11.706%	$67.7609	$67.76	$67.75	$67.80
Purchase #6	$162.65	5.428%	$171.4786	$171.48	$171.50	$171.50
Purchase #7	$77.55	6.387%	$82.5031	$82.50	$82.50	$82.50
7 purchase totals =	$998.86		$1,071.6035	$1,071.60	$1,071.60	$1,071.70