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	$89.76	9.656%	$98.4272	$98.43	$98.45	$98.40
Purchase #2	$227.61	7.668%	$245.0631	$245.06	$245.05	$245.10
Purchase #3	$149.48	4.518%	$156.2335	$156.23	$156.25	$156.20
Purchase #4	$81.53	3.714%	$84.558	$84.56	$84.55	$84.60
Purchase #5	$72.80	13.309%	$82.489	$82.49	$82.50	$82.50
Purchase #6	$16.57	6.767%	$17.6913	$17.69	$17.70	$17.70
Purchase #7	$37.63	12.757%	$42.4305	$42.43	$42.45	$42.40
7 purchase totals =	$675.38		$726.8926	$726.89	$726.95	$726.90