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	$226.78	10.123%	$249.7369	$249.74	$249.75	$249.70
Purchase #2	$144.63	3.763%	$150.0724	$150.07	$150.05	$150.10
Purchase #3	$95.71	4.219%	$99.748	$99.75	$99.75	$99.70
Purchase #4	$176.55	11.208%	$196.3377	$196.34	$196.35	$196.30
Purchase #5	$196.66	3.279%	$203.1085	$203.11	$203.10	$203.10
Purchase #6	$41.66	10.186%	$45.9035	$45.90	$45.90	$45.90
Purchase #7	$216.71	6.669%	$231.1624	$231.16	$231.15	$231.20
7 purchase totals =	$1,098.70		$1,176.0694	$1,176.07	$1,176.05	$1,176.00