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	$78.86	8.662%	$85.6909	$85.69	$85.70	$85.70
Purchase #2	$79.90	13.637%	$90.796	$90.80	$90.80	$90.80
Purchase #3	$170.43	3.415%	$176.2502	$176.25	$176.25	$176.30
Purchase #4	$101.40	6.574%	$108.066	$108.07	$108.05	$108.10
Purchase #5	$168.90	5.692%	$178.5138	$178.51	$178.50	$178.50
Purchase #6	$41.47	10.235%	$45.7145	$45.71	$45.70	$45.70
Purchase #7	$242.73	8.405%	$263.1315	$263.13	$263.15	$263.10
7 purchase totals =	$883.69		$948.1629	$948.16	$948.15	$948.20