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	$67.27	9.253%	$73.4945	$73.49	$73.50	$73.50
Purchase #2	$87.85	7.586%	$94.5143	$94.51	$94.50	$94.50
Purchase #3	$244.88	11.657%	$273.4257	$273.43	$273.45	$273.40
Purchase #4	$125.50	5.787%	$132.7627	$132.76	$132.75	$132.80
Purchase #5	$89.57	6.221%	$95.1421	$95.14	$95.15	$95.10
Purchase #6	$225.91	12.853%	$254.9462	$254.95	$254.95	$254.90
Purchase #7	$152.84	11.428%	$170.3066	$170.31	$170.30	$170.30
7 purchase totals =	$993.82		$1,094.5921	$1,094.59	$1,094.60	$1,094.50