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	$37.61	8.493%	$40.8042	$40.80	$40.80	$40.80
Purchase #2	$170.85	8.728%	$185.7618	$185.76	$185.75	$185.80
Purchase #3	$158.26	10.850%	$175.4312	$175.43	$175.45	$175.40
Purchase #4	$154.77	7.191%	$165.8995	$165.90	$165.90	$165.90
Purchase #5	$156.51	7.675%	$168.5221	$168.52	$168.50	$168.50
Purchase #6	$142.89	5.183%	$150.296	$150.30	$150.30	$150.30
Purchase #7	$243.99	8.239%	$264.0923	$264.09	$264.10	$264.10
7 purchase totals =	$1,064.88		$1,150.8071	$1,150.80	$1,150.80	$1,150.80