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	$71.74	5.639%	$75.7854	$75.79	$75.80	$75.80
Purchase #2	$216.89	5.808%	$229.487	$229.49	$229.50	$229.50
Purchase #3	$249.39	10.256%	$274.9674	$274.97	$274.95	$275.00
Purchase #4	$46.84	5.713%	$49.516	$49.52	$49.50	$49.50
Purchase #5	$151.82	9.266%	$165.8876	$165.89	$165.90	$165.90
Purchase #6	$19.45	4.313%	$20.2889	$20.29	$20.30	$20.30
Purchase #7	$79.36	12.809%	$89.5252	$89.53	$89.55	$89.50
7 purchase totals =	$835.49		$905.4575	$905.48	$905.50	$905.50