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	$44.66	8.204%	$48.3239	$48.32	$48.30	$48.30
Purchase #2	$133.33	13.511%	$151.3442	$151.34	$151.35	$151.30
Purchase #3	$26.88	4.835%	$28.1796	$28.18	$28.20	$28.20
Purchase #4	$183.38	6.382%	$195.0833	$195.08	$195.10	$195.10
Purchase #5	$84.82	5.480%	$89.4681	$89.47	$89.45	$89.50
Purchase #6	$83.57	12.820%	$94.2837	$94.28	$94.30	$94.30
Purchase #7	$200.25	8.283%	$216.8367	$216.84	$216.85	$216.80
7 purchase totals =	$756.89		$823.5195	$823.51	$823.55	$823.50