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	$181.96	8.204%	$196.888	$196.89	$196.90	$196.90
Purchase #2	$236.41	7.623%	$254.4315	$254.43	$254.45	$254.40
Purchase #3	$232.38	5.627%	$245.456	$245.46	$245.45	$245.50
Purchase #4	$146.27	3.174%	$150.9126	$150.91	$150.90	$150.90
Purchase #5	$139.84	9.754%	$153.48	$153.48	$153.50	$153.50
Purchase #6	$152.63	12.755%	$172.098	$172.10	$172.10	$172.10
Purchase #7	$13.70	12.622%	$15.4292	$15.43	$15.45	$15.40
7 purchase totals =	$1,103.19		$1,188.6953	$1,188.70	$1,188.75	$1,188.70