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	$207.37	3.438%	$214.4994	$214.50	$214.50	$214.50
Purchase #2	$22.65	6.812%	$24.1929	$24.19	$24.20	$24.20
Purchase #3	$34.74	8.192%	$37.5859	$37.59	$37.60	$37.60
Purchase #4	$92.71	7.422%	$99.5909	$99.59	$99.60	$99.60
Purchase #5	$83.93	8.214%	$90.824	$90.82	$90.80	$90.80
Purchase #6	$82.81	11.595%	$92.4118	$92.41	$92.40	$92.40
Purchase #7	$41.62	4.672%	$43.5645	$43.56	$43.55	$43.60
7 purchase totals =	$565.83		$602.6694	$602.66	$602.65	$602.70