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	$139.46	4.559%	$145.818	$145.82	$145.80	$145.80
Purchase #2	$179.32	7.202%	$192.2346	$192.23	$192.25	$192.20
Purchase #3	$167.60	8.319%	$181.5426	$181.54	$181.55	$181.50
Purchase #4	$138.42	12.686%	$155.98	$155.98	$156.00	$156.00
Purchase #5	$179.57	8.289%	$194.4546	$194.45	$194.45	$194.50
Purchase #6	$203.41	6.489%	$216.6093	$216.61	$216.60	$216.60
Purchase #7	$173.74	8.710%	$188.8728	$188.87	$188.85	$188.90
7 purchase totals =	$1,181.52		$1,275.5119	$1,275.50	$1,275.50	$1,275.50