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	$236.91	7.601%	$254.9175	$254.92	$254.90	$254.90
Purchase #2	$209.56	3.257%	$216.3854	$216.39	$216.40	$216.40
Purchase #3	$85.51	5.522%	$90.2319	$90.23	$90.25	$90.20
Purchase #4	$190.64	9.824%	$209.3685	$209.37	$209.35	$209.40
Purchase #5	$221.83	5.306%	$233.6003	$233.60	$233.60	$233.60
Purchase #6	$62.54	4.177%	$65.1523	$65.15	$65.15	$65.20
Purchase #7	$89.60	11.506%	$99.9094	$99.91	$99.90	$99.90
7 purchase totals =	$1,096.59		$1,169.5653	$1,169.57	$1,169.55	$1,169.60