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	$99.93	8.508%	$108.432	$108.43	$108.45	$108.40
Purchase #2	$223.52	13.746%	$254.2451	$254.25	$254.25	$254.20
Purchase #3	$234.88	13.819%	$267.3381	$267.34	$267.35	$267.30
Purchase #4	$128.78	5.449%	$135.7972	$135.80	$135.80	$135.80
Purchase #5	$79.70	12.788%	$89.892	$89.89	$89.90	$89.90
Purchase #6	$36.39	10.647%	$40.2644	$40.26	$40.25	$40.30
Purchase #7	$190.77	9.801%	$209.4674	$209.47	$209.45	$209.50
7 purchase totals =	$993.97		$1,105.4362	$1,105.44	$1,105.45	$1,105.40