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	$34.31	3.348%	$35.4587	$35.46	$35.45	$35.50
Purchase #2	$81.85	9.803%	$89.8738	$89.87	$89.85	$89.90
Purchase #3	$7.28	13.267%	$8.2458	$8.25	$8.25	$8.20
Purchase #4	$129.88	8.225%	$140.5626	$140.56	$140.55	$140.60
Purchase #5	$63.33	12.869%	$71.4799	$71.48	$71.50	$71.50
Purchase #6	$85.49	5.225%	$89.9569	$89.96	$89.95	$90.00
Purchase #7	$209.74	3.843%	$217.8003	$217.80	$217.80	$217.80
7 purchase totals =	$611.88		$653.3780	$653.38	$653.35	$653.50