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	$89.65	8.735%	$97.4809	$97.48	$97.50	$97.50
Purchase #2	$45.77	3.693%	$47.4603	$47.46	$47.45	$47.50
Purchase #3	$12.35	7.782%	$13.3111	$13.31	$13.30	$13.30
Purchase #4	$242.98	12.377%	$273.0536	$273.05	$273.05	$273.10
Purchase #5	$74.77	4.705%	$78.2879	$78.29	$78.30	$78.30
Purchase #6	$155.51	7.551%	$167.2526	$167.25	$167.25	$167.30
Purchase #7	$19.54	4.619%	$20.4426	$20.44	$20.45	$20.40
7 purchase totals =	$640.57		$697.2890	$697.28	$697.30	$697.40