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	$231.40	7.496%	$248.7457	$248.75	$248.75	$248.70
Purchase #2	$82.29	12.629%	$92.6824	$92.68	$92.70	$92.70
Purchase #3	$43.91	8.441%	$47.6164	$47.62	$47.60	$47.60
Purchase #4	$79.82	8.807%	$86.8497	$86.85	$86.85	$86.80
Purchase #5	$167.41	12.612%	$188.5237	$188.52	$188.50	$188.50
Purchase #6	$182.72	9.172%	$199.4791	$199.48	$199.50	$199.50
Purchase #7	$145.52	7.510%	$156.4486	$156.45	$156.45	$156.40
7 purchase totals =	$933.07		$1,020.3456	$1,020.35	$1,020.35	$1,020.20