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	$98.38	10.751%	$108.9568	$108.96	$108.95	$109.00
Purchase #2	$87.91	3.361%	$90.8647	$90.86	$90.85	$90.90
Purchase #3	$52.38	11.250%	$58.2728	$58.27	$58.25	$58.30
Purchase #4	$247.53	5.259%	$260.5476	$260.55	$260.55	$260.50
Purchase #5	$229.56	10.366%	$253.3562	$253.36	$253.35	$253.40
Purchase #6	$83.74	8.129%	$90.5472	$90.55	$90.55	$90.50
Purchase #7	$198.37	10.339%	$218.8795	$218.88	$218.90	$218.90
7 purchase totals =	$997.87		$1,081.4248	$1,081.43	$1,081.40	$1,081.50