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	$213.71	11.722%	$238.7611	$238.76	$238.75	$238.80
Purchase #2	$75.25	11.473%	$83.8834	$83.88	$83.90	$83.90
Purchase #3	$229.93	10.662%	$254.4451	$254.45	$254.45	$254.40
Purchase #4	$250.56	7.567%	$269.5199	$269.52	$269.50	$269.50
Purchase #5	$170.92	8.771%	$185.9114	$185.91	$185.90	$185.90
Purchase #6	$164.37	13.692%	$186.8755	$186.88	$186.90	$186.90
Purchase #7	$111.71	5.734%	$118.1155	$118.12	$118.10	$118.10
7 purchase totals =	$1,216.45		$1,337.5119	$1,337.52	$1,337.50	$1,337.50