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	$196.29	12.737%	$221.2915	$221.29	$221.30	$221.30
Purchase #2	$215.53	11.716%	$240.7815	$240.78	$240.80	$240.80
Purchase #3	$244.69	7.333%	$262.6331	$262.63	$262.65	$262.60
Purchase #4	$122.46	13.564%	$139.0705	$139.07	$139.05	$139.10
Purchase #5	$229.43	7.362%	$246.3206	$246.32	$246.30	$246.30
Purchase #6	$65.55	9.570%	$71.8231	$71.82	$71.80	$71.80
Purchase #7	$220.62	12.415%	$248.01	$248.01	$248.00	$248.00
7 purchase totals =	$1,294.57		$1,429.9303	$1,429.92	$1,429.90	$1,429.90