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	$56.49	9.633%	$61.9317	$61.93	$61.95	$61.90
Purchase #2	$235.31	8.297%	$254.8337	$254.83	$254.85	$254.80
Purchase #3	$137.72	9.114%	$150.2718	$150.27	$150.25	$150.30
Purchase #4	$232.59	6.325%	$247.3013	$247.30	$247.30	$247.30
Purchase #5	$232.83	7.563%	$250.4389	$250.44	$250.45	$250.40
Purchase #6	$121.71	13.644%	$138.3161	$138.32	$138.30	$138.30
Purchase #7	$37.45	10.131%	$41.2441	$41.24	$41.25	$41.20
7 purchase totals =	$1,054.10		$1,144.3376	$1,144.33	$1,144.35	$1,144.20