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	$73.49	12.350%	$82.566	$82.57	$82.55	$82.60
Purchase #2	$171.51	12.451%	$192.8647	$192.86	$192.85	$192.90
Purchase #3	$128.42	11.283%	$142.9096	$142.91	$142.90	$142.90
Purchase #4	$171.75	12.180%	$192.6692	$192.67	$192.65	$192.70
Purchase #5	$9.29	10.185%	$10.2362	$10.24	$10.25	$10.20
Purchase #6	$120.43	6.693%	$128.4904	$128.49	$128.50	$128.50
Purchase #7	$93.36	5.423%	$98.4229	$98.42	$98.40	$98.40
7 purchase totals =	$768.25		$848.1590	$848.16	$848.10	$848.20