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	$122.86	6.653%	$131.0339	$131.03	$131.05	$131.00
Purchase #2	$115.83	4.121%	$120.6034	$120.60	$120.60	$120.60
Purchase #3	$162.76	7.646%	$175.2046	$175.20	$175.20	$175.20
Purchase #4	$100.45	11.142%	$111.6421	$111.64	$111.65	$111.60
Purchase #5	$157.42	3.223%	$162.4936	$162.49	$162.50	$162.50
Purchase #6	$6.46	10.790%	$7.157	$7.16	$7.15	$7.20
Purchase #7	$57.33	11.770%	$64.0777	$64.08	$64.10	$64.10
7 purchase totals =	$723.11		$772.2123	$772.20	$772.25	$772.20