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	$155.97	11.213%	$173.4589	$173.46	$173.45	$173.50
Purchase #2	$82.25	12.219%	$92.3001	$92.30	$92.30	$92.30
Purchase #3	$173.42	12.730%	$195.4964	$195.50	$195.50	$195.50
Purchase #4	$162.72	7.643%	$175.1567	$175.16	$175.15	$175.20
Purchase #5	$164.41	12.449%	$184.8774	$184.88	$184.90	$184.90
Purchase #6	$93.72	12.592%	$105.5212	$105.52	$105.50	$105.50
Purchase #7	$200.41	8.592%	$217.6292	$217.63	$217.65	$217.60
7 purchase totals =	$1,032.90		$1,144.4399	$1,144.45	$1,144.45	$1,144.50