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	$244.51	4.813%	$256.2783	$256.28	$256.30	$256.30
Purchase #2	$198.53	7.279%	$212.981	$212.98	$213.00	$213.00
Purchase #3	$148.93	7.674%	$160.3589	$160.36	$160.35	$160.40
Purchase #4	$134.35	6.714%	$143.3703	$143.37	$143.35	$143.40
Purchase #5	$40.79	5.210%	$42.9152	$42.92	$42.90	$42.90
Purchase #6	$172.76	10.523%	$190.9395	$190.94	$190.95	$190.90
Purchase #7	$154.93	8.322%	$167.8233	$167.82	$167.80	$167.80
7 purchase totals =	$1,094.80		$1,174.6665	$1,174.67	$1,174.65	$1,174.70