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	$122.78	7.477%	$131.9603	$131.96	$131.95	$132.00
Purchase #2	$92.35	6.767%	$98.5993	$98.60	$98.60	$98.60
Purchase #3	$204.93	9.490%	$224.3779	$224.38	$224.40	$224.40
Purchase #4	$122.53	7.228%	$131.3865	$131.39	$131.40	$131.40
Purchase #5	$112.53	13.224%	$127.411	$127.41	$127.40	$127.40
Purchase #6	$157.52	9.180%	$171.9803	$171.98	$172.00	$172.00
Purchase #7	$61.52	6.578%	$65.5668	$65.57	$65.55	$65.60
7 purchase totals =	$874.16		$951.2821	$951.29	$951.30	$951.40