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	$190.72	9.440%	$208.724	$208.72	$208.70	$208.70
Purchase #2	$120.82	3.129%	$124.6005	$124.60	$124.60	$124.60
Purchase #3	$156.63	11.357%	$174.4185	$174.42	$174.40	$174.40
Purchase #4	$34.66	13.801%	$39.4434	$39.44	$39.45	$39.40
Purchase #5	$224.32	8.291%	$242.9184	$242.92	$242.90	$242.90
Purchase #6	$146.71	4.151%	$152.7999	$152.80	$152.80	$152.80
Purchase #7	$55.26	9.168%	$60.3262	$60.33	$60.35	$60.30
7 purchase totals =	$929.12		$1,003.2309	$1,003.23	$1,003.20	$1,003.10