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	$22.84	6.230%	$24.2629	$24.26	$24.25	$24.30
Purchase #2	$113.93	4.728%	$119.3166	$119.32	$119.30	$119.30
Purchase #3	$80.58	11.350%	$89.7258	$89.73	$89.75	$89.70
Purchase #4	$33.81	4.834%	$35.4444	$35.44	$35.45	$35.40
Purchase #5	$117.78	5.725%	$124.5229	$124.52	$124.50	$124.50
Purchase #6	$215.58	3.547%	$223.2266	$223.23	$223.25	$223.20
Purchase #7	$143.49	8.806%	$156.1257	$156.13	$156.15	$156.10
7 purchase totals =	$728.01		$772.6249	$772.63	$772.65	$772.50