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	$50.49	3.627%	$52.3213	$52.32	$52.30	$52.30
Purchase #2	$233.92	8.801%	$254.5073	$254.51	$254.50	$254.50
Purchase #3	$37.41	8.204%	$40.4791	$40.48	$40.50	$40.50
Purchase #4	$38.36	11.598%	$42.809	$42.81	$42.80	$42.80
Purchase #5	$184.60	11.222%	$205.3158	$205.32	$205.30	$205.30
Purchase #6	$113.29	10.124%	$124.7595	$124.76	$124.75	$124.80
Purchase #7	$49.45	8.617%	$53.7111	$53.71	$53.70	$53.70
7 purchase totals =	$707.52		$773.9031	$773.91	$773.85	$773.90