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	$152.40	13.243%	$172.5823	$172.58	$172.60	$172.60
Purchase #2	$6.73	13.170%	$7.6163	$7.62	$7.60	$7.60
Purchase #3	$188.93	12.434%	$212.4216	$212.42	$212.40	$212.40
Purchase #4	$231.35	4.842%	$242.552	$242.55	$242.55	$242.60
Purchase #5	$191.61	13.165%	$216.8355	$216.84	$216.85	$216.80
Purchase #6	$116.55	12.488%	$131.1048	$131.10	$131.10	$131.10
Purchase #7	$59.53	6.758%	$63.553	$63.55	$63.55	$63.60
7 purchase totals =	$947.10		$1,046.6655	$1,046.66	$1,046.65	$1,046.70