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	$189.84	5.447%	$200.1806	$200.18	$200.20	$200.20
Purchase #2	$134.43	13.143%	$152.0981	$152.10	$152.10	$152.10
Purchase #3	$166.69	4.113%	$173.546	$173.55	$173.55	$173.50
Purchase #4	$27.58	11.138%	$30.6519	$30.65	$30.65	$30.70
Purchase #5	$219.83	10.153%	$242.1493	$242.15	$242.15	$242.10
Purchase #6	$73.73	7.707%	$79.4124	$79.41	$79.40	$79.40
Purchase #7	$204.47	8.820%	$222.5043	$222.50	$222.50	$222.50
7 purchase totals =	$1,016.57		$1,100.5426	$1,100.54	$1,100.55	$1,100.50