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	$222.60	8.639%	$241.8304	$241.83	$241.85	$241.80
Purchase #2	$232.92	3.223%	$240.427	$240.43	$240.45	$240.40
Purchase #3	$48.89	6.161%	$51.9021	$51.90	$51.90	$51.90
Purchase #4	$40.81	12.342%	$45.8468	$45.85	$45.85	$45.80
Purchase #5	$68.84	6.865%	$73.5659	$73.57	$73.55	$73.60
Purchase #6	$218.54	5.112%	$229.7118	$229.71	$229.70	$229.70
Purchase #7	$142.58	3.785%	$147.9767	$147.98	$148.00	$148.00
7 purchase totals =	$975.18		$1,031.2607	$1,031.27	$1,031.30	$1,031.20