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	$115.74	12.755%	$130.5026	$130.50	$130.50	$130.50
Purchase #2	$44.42	3.115%	$45.8037	$45.80	$45.80	$45.80
Purchase #3	$125.59	10.725%	$139.0595	$139.06	$139.05	$139.10
Purchase #4	$222.78	11.284%	$247.9185	$247.92	$247.90	$247.90
Purchase #5	$190.96	4.529%	$199.6086	$199.61	$199.60	$199.60
Purchase #6	$104.83	5.493%	$110.5883	$110.59	$110.60	$110.60
Purchase #7	$183.49	3.171%	$189.3085	$189.31	$189.30	$189.30
7 purchase totals =	$987.81		$1,062.7897	$1,062.79	$1,062.75	$1,062.80