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	$8.75	9.858%	$9.6126	$9.61	$9.60	$9.60
Purchase #2	$189.53	3.805%	$196.7416	$196.74	$196.75	$196.70
Purchase #3	$233.64	5.762%	$247.1023	$247.10	$247.10	$247.10
Purchase #4	$201.36	10.510%	$222.5229	$222.52	$222.50	$222.50
Purchase #5	$197.58	12.304%	$221.8902	$221.89	$221.90	$221.90
Purchase #6	$110.39	9.172%	$120.515	$120.52	$120.50	$120.50
Purchase #7	$40.39	8.523%	$43.8324	$43.83	$43.85	$43.80
7 purchase totals =	$981.64		$1,062.2170	$1,062.21	$1,062.20	$1,062.10