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	$105.82	11.572%	$118.0655	$118.07	$118.05	$118.10
Purchase #2	$95.95	12.602%	$108.0416	$108.04	$108.05	$108.00
Purchase #3	$83.25	6.144%	$88.3649	$88.36	$88.35	$88.40
Purchase #4	$32.62	11.587%	$36.3997	$36.40	$36.40	$36.40
Purchase #5	$118.75	3.585%	$123.0072	$123.01	$123.00	$123.00
Purchase #6	$113.50	13.385%	$128.692	$128.69	$128.70	$128.70
Purchase #7	$80.41	4.242%	$83.821	$83.82	$83.80	$83.80
7 purchase totals =	$630.30		$686.3919	$686.39	$686.35	$686.40