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	$48.44	11.281%	$53.9045	$53.90	$53.90	$53.90
Purchase #2	$74.38	8.294%	$80.5491	$80.55	$80.55	$80.50
Purchase #3	$48.78	7.591%	$52.4829	$52.48	$52.50	$52.50
Purchase #4	$143.72	8.207%	$155.5151	$155.52	$155.50	$155.50
Purchase #5	$81.73	11.153%	$90.8453	$90.85	$90.85	$90.80
Purchase #6	$133.61	7.817%	$144.0543	$144.05	$144.05	$144.10
Purchase #7	$213.50	10.250%	$235.3838	$235.38	$235.40	$235.40
7 purchase totals =	$744.16		$812.7350	$812.73	$812.75	$812.70