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	$54.92	8.765%	$59.7337	$59.73	$59.75	$59.70
Purchase #2	$241.94	5.517%	$255.2878	$255.29	$255.30	$255.30
Purchase #3	$121.56	4.285%	$126.7688	$126.77	$126.75	$126.80
Purchase #4	$27.80	9.868%	$30.5433	$30.54	$30.55	$30.50
Purchase #5	$90.53	7.285%	$97.1251	$97.13	$97.15	$97.10
Purchase #6	$55.87	10.134%	$61.5319	$61.53	$61.55	$61.50
Purchase #7	$152.39	8.760%	$165.7394	$165.74	$165.75	$165.70
7 purchase totals =	$745.01		$796.7300	$796.73	$796.80	$796.60