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	$203.82	5.629%	$215.293	$215.29	$215.30	$215.30
Purchase #2	$35.25	13.843%	$40.1297	$40.13	$40.15	$40.10
Purchase #3	$61.57	7.436%	$66.1483	$66.15	$66.15	$66.10
Purchase #4	$22.52	6.830%	$24.0581	$24.06	$24.05	$24.10
Purchase #5	$11.62	5.295%	$12.2353	$12.24	$12.25	$12.20
Purchase #6	$99.81	3.470%	$103.2734	$103.27	$103.25	$103.30
Purchase #7	$233.34	9.236%	$254.8913	$254.89	$254.90	$254.90
7 purchase totals =	$667.93		$716.0291	$716.03	$716.05	$716.00