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	$59.38	13.335%	$67.2983	$67.30	$67.30	$67.30
Purchase #2	$21.28	11.823%	$23.7959	$23.80	$23.80	$23.80
Purchase #3	$212.55	12.420%	$238.9487	$238.95	$238.95	$238.90
Purchase #4	$169.56	10.576%	$187.4927	$187.49	$187.50	$187.50
Purchase #5	$178.69	5.428%	$188.3893	$188.39	$188.40	$188.40
Purchase #6	$150.91	7.790%	$162.6659	$162.67	$162.65	$162.70
Purchase #7	$99.78	4.857%	$104.6263	$104.63	$104.65	$104.60
7 purchase totals =	$892.15		$973.2171	$973.23	$973.25	$973.20