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	$32.43	9.736%	$35.5874	$35.59	$35.60	$35.60
Purchase #2	$93.92	9.292%	$102.647	$102.65	$102.65	$102.60
Purchase #3	$63.81	13.352%	$72.3299	$72.33	$72.35	$72.30
Purchase #4	$9.45	11.507%	$10.5374	$10.54	$10.55	$10.50
Purchase #5	$80.63	3.301%	$83.2916	$83.29	$83.30	$83.30
Purchase #6	$51.95	13.296%	$58.8573	$58.86	$58.85	$58.90
Purchase #7	$185.73	7.374%	$199.4257	$199.43	$199.45	$199.40
7 purchase totals =	$517.92		$562.6763	$562.69	$562.75	$562.60