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	$238.47	7.510%	$256.3791	$256.38	$256.40	$256.40
Purchase #2	$39.56	7.595%	$42.5646	$42.56	$42.55	$42.60
Purchase #3	$165.73	11.557%	$184.8834	$184.88	$184.90	$184.90
Purchase #4	$150.47	10.361%	$166.0602	$166.06	$166.05	$166.10
Purchase #5	$76.41	13.849%	$86.992	$86.99	$87.00	$87.00
Purchase #6	$89.48	9.529%	$98.0065	$98.01	$98.00	$98.00
Purchase #7	$45.61	12.726%	$51.4143	$51.41	$51.40	$51.40
7 purchase totals =	$805.73		$886.3001	$886.29	$886.30	$886.40