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	$231.77	8.583%	$251.6628	$251.66	$251.65	$251.70
Purchase #2	$169.36	9.532%	$185.5034	$185.50	$185.50	$185.50
Purchase #3	$82.39	8.111%	$89.0727	$89.07	$89.05	$89.10
Purchase #4	$142.30	5.818%	$150.579	$150.58	$150.60	$150.60
Purchase #5	$134.51	3.116%	$138.7013	$138.70	$138.70	$138.70
Purchase #6	$110.61	11.180%	$122.9762	$122.98	$123.00	$123.00
Purchase #7	$137.41	3.517%	$142.2427	$142.24	$142.25	$142.20
7 purchase totals =	$1,008.35		$1,080.7381	$1,080.73	$1,080.75	$1,080.80