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	$103.83	8.333%	$112.4822	$112.48	$112.50	$112.50
Purchase #2	$113.72	12.400%	$127.8213	$127.82	$127.80	$127.80
Purchase #3	$79.65	8.838%	$86.6895	$86.69	$86.70	$86.70
Purchase #4	$53.60	12.132%	$60.1028	$60.10	$60.10	$60.10
Purchase #5	$168.69	5.640%	$178.2041	$178.20	$178.20	$178.20
Purchase #6	$63.78	13.356%	$72.2985	$72.30	$72.30	$72.30
Purchase #7	$47.53	6.485%	$50.6123	$50.61	$50.60	$50.60
7 purchase totals =	$630.80		$688.2107	$688.20	$688.20	$688.20