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	$85.47	11.667%	$95.4418	$95.44	$95.45	$95.40
Purchase #2	$167.54	12.517%	$188.511	$188.51	$188.50	$188.50
Purchase #3	$83.55	5.656%	$88.2756	$88.28	$88.30	$88.30
Purchase #4	$61.30	13.132%	$69.3499	$69.35	$69.35	$69.30
Purchase #5	$65.74	9.271%	$71.8348	$71.83	$71.85	$71.80
Purchase #6	$88.54	3.850%	$91.9488	$91.95	$91.95	$91.90
Purchase #7	$230.84	12.858%	$260.5214	$260.52	$260.50	$260.50
7 purchase totals =	$782.98		$865.8833	$865.88	$865.90	$865.70