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	$242.95	5.225%	$255.6441	$255.64	$255.65	$255.60
Purchase #2	$33.66	7.108%	$36.0526	$36.05	$36.05	$36.10
Purchase #3	$119.55	11.345%	$133.1129	$133.11	$133.10	$133.10
Purchase #4	$218.69	6.657%	$233.2482	$233.25	$233.25	$233.20
Purchase #5	$178.85	12.254%	$200.7663	$200.77	$200.75	$200.80
Purchase #6	$176.73	7.233%	$189.5129	$189.51	$189.50	$189.50
Purchase #7	$130.44	10.869%	$144.6175	$144.62	$144.60	$144.60
7 purchase totals =	$1,100.87		$1,192.9545	$1,192.95	$1,192.90	$1,192.90