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	$239.81	6.236%	$254.7646	$254.76	$254.75	$254.80
Purchase #2	$169.48	6.133%	$179.8742	$179.87	$179.85	$179.90
Purchase #3	$87.48	13.775%	$99.5304	$99.53	$99.55	$99.50
Purchase #4	$166.35	12.374%	$186.9341	$186.93	$186.95	$186.90
Purchase #5	$122.89	4.140%	$127.9776	$127.98	$128.00	$128.00
Purchase #6	$87.33	13.408%	$99.0392	$99.04	$99.05	$99.00
Purchase #7	$86.90	13.258%	$98.4212	$98.42	$98.40	$98.40
7 purchase totals =	$960.24		$1,046.5413	$1,046.53	$1,046.55	$1,046.50