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	$43.32	4.147%	$45.1165	$45.12	$45.10	$45.10
Purchase #2	$46.60	10.780%	$51.6235	$51.62	$51.60	$51.60
Purchase #3	$179.84	12.355%	$202.0592	$202.06	$202.05	$202.10
Purchase #4	$198.86	13.459%	$225.6246	$225.62	$225.60	$225.60
Purchase #5	$222.43	12.327%	$249.8489	$249.85	$249.85	$249.80
Purchase #6	$199.85	12.643%	$225.117	$225.12	$225.10	$225.10
Purchase #7	$88.53	13.699%	$100.6577	$100.66	$100.65	$100.70
7 purchase totals =	$979.43		$1,100.0474	$1,100.05	$1,099.95	$1,100.00