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	$40.37	6.234%	$42.8867	$42.89	$42.90	$42.90
Purchase #2	$245.94	9.503%	$269.3117	$269.31	$269.30	$269.30
Purchase #3	$35.37	9.426%	$38.704	$38.70	$38.70	$38.70
Purchase #4	$243.47	4.755%	$255.047	$255.05	$255.05	$255.00
Purchase #5	$227.96	7.282%	$244.56	$244.56	$244.55	$244.60
Purchase #6	$10.86	13.610%	$12.338	$12.34	$12.35	$12.30
Purchase #7	$171.58	7.199%	$183.932	$183.93	$183.95	$183.90
7 purchase totals =	$975.55		$1,046.7794	$1,046.78	$1,046.80	$1,046.70