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	$131.39	4.820%	$137.723	$137.72	$137.70	$137.70
Purchase #2	$90.84	7.691%	$97.8265	$97.83	$97.85	$97.80
Purchase #3	$161.46	7.872%	$174.1701	$174.17	$174.15	$174.20
Purchase #4	$52.41	6.279%	$55.7008	$55.70	$55.70	$55.70
Purchase #5	$54.30	10.227%	$59.8533	$59.85	$59.85	$59.90
Purchase #6	$50.66	6.253%	$53.8278	$53.83	$53.85	$53.80
Purchase #7	$173.29	11.674%	$193.5199	$193.52	$193.50	$193.50
7 purchase totals =	$714.35		$772.6214	$772.62	$772.60	$772.60