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	$192.55	9.558%	$210.9539	$210.95	$210.95	$211.00
Purchase #2	$21.97	11.640%	$24.5273	$24.53	$24.55	$24.50
Purchase #3	$213.56	4.598%	$223.3795	$223.38	$223.40	$223.40
Purchase #4	$98.57	13.374%	$111.7528	$111.75	$111.75	$111.80
Purchase #5	$246.58	7.584%	$265.2806	$265.28	$265.30	$265.30
Purchase #6	$34.73	5.146%	$36.5172	$36.52	$36.50	$36.50
Purchase #7	$124.31	7.449%	$133.5699	$133.57	$133.55	$133.60
7 purchase totals =	$932.27		$1,005.9812	$1,005.98	$1,006.00	$1,006.10