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	$223.53	13.402%	$253.4875	$253.49	$253.50	$253.50
Purchase #2	$57.30	10.632%	$63.3921	$63.39	$63.40	$63.40
Purchase #3	$89.34	6.482%	$95.131	$95.13	$95.15	$95.10
Purchase #4	$189.54	5.533%	$200.0272	$200.03	$200.05	$200.00
Purchase #5	$223.37	13.635%	$253.8265	$253.83	$253.85	$253.80
Purchase #6	$32.35	7.454%	$34.7614	$34.76	$34.75	$34.80
Purchase #7	$104.80	6.608%	$111.7252	$111.73	$111.75	$111.70
7 purchase totals =	$920.23		$1,012.3509	$1,012.36	$1,012.45	$1,012.30