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	$185.83	7.588%	$199.9308	$199.93	$199.95	$199.90
Purchase #2	$124.84	5.498%	$131.7037	$131.70	$131.70	$131.70
Purchase #3	$134.33	12.727%	$151.4262	$151.43	$151.45	$151.40
Purchase #4	$213.47	3.600%	$221.1549	$221.15	$221.15	$221.20
Purchase #5	$134.62	7.173%	$144.2763	$144.28	$144.30	$144.30
Purchase #6	$80.77	10.558%	$89.2977	$89.30	$89.30	$89.30
Purchase #7	$171.37	3.103%	$176.6876	$176.69	$176.70	$176.70
7 purchase totals =	$1,045.23		$1,114.4772	$1,114.48	$1,114.55	$1,114.50