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	$139.45	11.135%	$154.9778	$154.98	$155.00	$155.00
Purchase #2	$92.31	7.713%	$99.4299	$99.43	$99.45	$99.40
Purchase #3	$141.39	13.776%	$160.8679	$160.87	$160.85	$160.90
Purchase #4	$154.95	8.753%	$168.5128	$168.51	$168.50	$168.50
Purchase #5	$188.34	5.429%	$198.565	$198.57	$198.55	$198.60
Purchase #6	$69.72	5.662%	$73.6675	$73.67	$73.65	$73.70
Purchase #7	$42.87	7.298%	$45.9987	$46.00	$46.00	$46.00
7 purchase totals =	$829.03		$902.0196	$902.03	$902.00	$902.10