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	$222.50	8.183%	$240.7072	$240.71	$240.70	$240.70
Purchase #2	$55.83	5.711%	$59.0185	$59.02	$59.00	$59.00
Purchase #3	$67.51	5.647%	$71.3223	$71.32	$71.30	$71.30
Purchase #4	$137.28	7.483%	$147.5527	$147.55	$147.55	$147.60
Purchase #5	$130.72	10.143%	$143.9789	$143.98	$144.00	$144.00
Purchase #6	$178.94	12.295%	$200.9407	$200.94	$200.95	$200.90
Purchase #7	$67.44	9.124%	$73.5932	$73.59	$73.60	$73.60
7 purchase totals =	$860.22		$937.1135	$937.11	$937.10	$937.10