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	$218.53	6.285%	$232.2646	$232.26	$232.25	$232.30
Purchase #2	$88.98	12.220%	$99.8534	$99.85	$99.85	$99.90
Purchase #3	$201.90	7.501%	$217.0445	$217.04	$217.05	$217.00
Purchase #4	$100.56	3.165%	$103.7427	$103.74	$103.75	$103.70
Purchase #5	$151.50	10.848%	$167.9347	$167.93	$167.95	$167.90
Purchase #6	$66.75	10.639%	$73.8515	$73.85	$73.85	$73.90
Purchase #7	$35.33	5.782%	$37.3728	$37.37	$37.35	$37.40
7 purchase totals =	$863.55		$932.0642	$932.04	$932.05	$932.10