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	$75.90	10.315%	$83.7291	$83.73	$83.75	$83.70
Purchase #2	$209.77	13.582%	$238.261	$238.26	$238.25	$238.30
Purchase #3	$158.81	6.120%	$168.5292	$168.53	$168.55	$168.50
Purchase #4	$250.61	5.537%	$264.4863	$264.49	$264.50	$264.50
Purchase #5	$229.87	3.781%	$238.5614	$238.56	$238.55	$238.60
Purchase #6	$66.34	7.832%	$71.5357	$71.54	$71.55	$71.50
Purchase #7	$214.55	10.254%	$236.55	$236.55	$236.55	$236.60
7 purchase totals =	$1,205.85		$1,301.6527	$1,301.66	$1,301.70	$1,301.70