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	$41.70	8.781%	$45.3617	$45.36	$45.35	$45.40
Purchase #2	$169.40	9.189%	$184.9662	$184.97	$184.95	$185.00
Purchase #3	$150.64	5.743%	$159.2913	$159.29	$159.30	$159.30
Purchase #4	$188.34	9.110%	$205.4978	$205.50	$205.50	$205.50
Purchase #5	$10.31	13.272%	$11.6783	$11.68	$11.70	$11.70
Purchase #6	$18.48	12.130%	$20.7216	$20.72	$20.70	$20.70
Purchase #7	$82.51	8.865%	$89.8245	$89.82	$89.80	$89.80
7 purchase totals =	$661.38		$717.3414	$717.34	$717.30	$717.40