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	$48.72	9.386%	$53.2929	$53.29	$53.30	$53.30
Purchase #2	$75.57	8.609%	$82.0758	$82.08	$82.10	$82.10
Purchase #3	$56.90	6.135%	$60.3908	$60.39	$60.40	$60.40
Purchase #4	$15.66	6.727%	$16.7134	$16.71	$16.70	$16.70
Purchase #5	$78.91	4.220%	$82.24	$82.24	$82.25	$82.20
Purchase #6	$97.61	10.745%	$108.0982	$108.10	$108.10	$108.10
Purchase #7	$41.28	10.256%	$45.5137	$45.51	$45.50	$45.50
7 purchase totals =	$414.65		$448.3248	$448.32	$448.35	$448.30