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	$114.83	13.528%	$130.3642	$130.36	$130.35	$130.40
Purchase #2	$52.96	11.874%	$59.2485	$59.25	$59.25	$59.20
Purchase #3	$61.46	4.305%	$64.1059	$64.11	$64.10	$64.10
Purchase #4	$243.65	4.186%	$253.8492	$253.85	$253.85	$253.80
Purchase #5	$170.72	13.641%	$194.0079	$194.01	$194.00	$194.00
Purchase #6	$168.66	8.182%	$182.4598	$182.46	$182.45	$182.50
Purchase #7	$206.62	13.470%	$234.4517	$234.45	$234.45	$234.50
7 purchase totals =	$1,018.90		$1,118.4872	$1,118.49	$1,118.45	$1,118.50