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	$250.64	4.651%	$262.2973	$262.30	$262.30	$262.30
Purchase #2	$174.87	7.333%	$187.6932	$187.69	$187.70	$187.70
Purchase #3	$179.85	12.492%	$202.3169	$202.32	$202.30	$202.30
Purchase #4	$39.67	4.667%	$41.5214	$41.52	$41.50	$41.50
Purchase #5	$52.89	11.625%	$59.0385	$59.04	$59.05	$59.00
Purchase #6	$37.48	13.390%	$42.4986	$42.50	$42.50	$42.50
Purchase #7	$248.31	13.494%	$281.817	$281.82	$281.80	$281.80
7 purchase totals =	$983.71		$1,077.1829	$1,077.19	$1,077.15	$1,077.10