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	$244.58	9.803%	$268.5562	$268.56	$268.55	$268.60
Purchase #2	$84.46	5.508%	$89.1121	$89.11	$89.10	$89.10
Purchase #3	$172.37	12.800%	$194.4334	$194.43	$194.45	$194.40
Purchase #4	$197.42	11.778%	$220.6721	$220.67	$220.65	$220.70
Purchase #5	$96.48	9.360%	$105.5105	$105.51	$105.50	$105.50
Purchase #6	$13.28	8.383%	$14.3933	$14.39	$14.40	$14.40
Purchase #7	$139.81	3.344%	$144.4852	$144.49	$144.50	$144.50
7 purchase totals =	$948.40		$1,037.1628	$1,037.16	$1,037.15	$1,037.20