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	$225.41	8.802%	$245.2506	$245.25	$245.25	$245.30
Purchase #2	$247.71	10.155%	$272.865	$272.87	$272.85	$272.90
Purchase #3	$106.45	11.788%	$118.9983	$119.00	$119.00	$119.00
Purchase #4	$196.88	7.378%	$211.4058	$211.41	$211.40	$211.40
Purchase #5	$37.38	11.797%	$41.7897	$41.79	$41.80	$41.80
Purchase #6	$85.29	13.317%	$96.6481	$96.65	$96.65	$96.60
Purchase #7	$30.91	3.308%	$31.9325	$31.93	$31.95	$31.90
7 purchase totals =	$930.03		$1,018.8900	$1,018.90	$1,018.90	$1,018.90