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	$187.96	11.401%	$209.3893	$209.39	$209.40	$209.40
Purchase #2	$157.62	4.866%	$165.2898	$165.29	$165.30	$165.30
Purchase #3	$203.79	10.528%	$225.245	$225.25	$225.25	$225.20
Purchase #4	$62.48	5.834%	$66.1251	$66.13	$66.15	$66.10
Purchase #5	$175.51	12.703%	$197.805	$197.81	$197.80	$197.80
Purchase #6	$85.62	4.405%	$89.3916	$89.39	$89.40	$89.40
Purchase #7	$54.38	4.843%	$57.0136	$57.01	$57.00	$57.00
7 purchase totals =	$927.36		$1,010.2594	$1,010.27	$1,010.30	$1,010.20