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	$52.91	4.586%	$55.3365	$55.34	$55.35	$55.30
Purchase #2	$249.86	11.304%	$278.1042	$278.10	$278.10	$278.10
Purchase #3	$42.99	6.233%	$45.6696	$45.67	$45.65	$45.70
Purchase #4	$207.59	8.339%	$224.9009	$224.90	$224.90	$224.90
Purchase #5	$192.46	8.379%	$208.5862	$208.59	$208.60	$208.60
Purchase #6	$223.64	7.808%	$241.1018	$241.10	$241.10	$241.10
Purchase #7	$144.60	8.508%	$156.9026	$156.90	$156.90	$156.90
7 purchase totals =	$1,114.05		$1,210.6018	$1,210.60	$1,210.60	$1,210.60