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	$72.64	8.207%	$78.6016	$78.60	$78.60	$78.60
Purchase #2	$179.60	5.706%	$189.848	$189.85	$189.85	$189.80
Purchase #3	$209.47	13.364%	$237.4636	$237.46	$237.45	$237.50
Purchase #4	$13.44	3.586%	$13.922	$13.92	$13.90	$13.90
Purchase #5	$165.94	13.372%	$188.1295	$188.13	$188.15	$188.10
Purchase #6	$155.82	10.807%	$172.6595	$172.66	$172.65	$172.70
Purchase #7	$209.38	3.561%	$216.836	$216.84	$216.85	$216.80
7 purchase totals =	$1,006.29		$1,097.4602	$1,097.46	$1,097.45	$1,097.40