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	$243.53	8.622%	$264.5272	$264.53	$264.55	$264.50
Purchase #2	$161.40	13.735%	$183.5683	$183.57	$183.55	$183.60
Purchase #3	$112.77	10.830%	$124.983	$124.98	$125.00	$125.00
Purchase #4	$220.44	8.206%	$238.5293	$238.53	$238.55	$238.50
Purchase #5	$114.79	11.371%	$127.8428	$127.84	$127.85	$127.80
Purchase #6	$166.54	6.633%	$177.5866	$177.59	$177.60	$177.60
Purchase #7	$77.72	7.362%	$83.4417	$83.44	$83.45	$83.40
7 purchase totals =	$1,097.19		$1,200.4789	$1,200.48	$1,200.55	$1,200.40