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	$33.58	13.361%	$38.0666	$38.07	$38.05	$38.10
Purchase #2	$88.38	5.631%	$93.3567	$93.36	$93.35	$93.40
Purchase #3	$100.54	12.220%	$112.826	$112.83	$112.85	$112.80
Purchase #4	$244.39	4.400%	$255.1432	$255.14	$255.15	$255.10
Purchase #5	$85.71	3.649%	$88.8376	$88.84	$88.85	$88.80
Purchase #6	$165.48	7.867%	$178.4983	$178.50	$178.50	$178.50
Purchase #7	$240.34	5.353%	$253.2054	$253.21	$253.20	$253.20
7 purchase totals =	$958.42		$1,019.9338	$1,019.95	$1,019.95	$1,019.90