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	$71.39	3.369%	$73.7951	$73.80	$73.80	$73.80
Purchase #2	$67.32	8.341%	$72.9352	$72.94	$72.95	$72.90
Purchase #3	$53.73	11.164%	$59.7284	$59.73	$59.75	$59.70
Purchase #4	$51.99	10.520%	$57.4593	$57.46	$57.45	$57.50
Purchase #5	$207.35	9.665%	$227.3904	$227.39	$227.40	$227.40
Purchase #6	$154.44	4.691%	$161.6848	$161.68	$161.70	$161.70
Purchase #7	$47.61	11.331%	$53.0047	$53.00	$53.00	$53.00
7 purchase totals =	$653.83		$705.9979	$706.00	$706.05	$706.00