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	$29.34	6.855%	$31.3513	$31.35	$31.35	$31.40
Purchase #2	$102.34	8.502%	$111.0409	$111.04	$111.05	$111.00
Purchase #3	$10.51	6.701%	$11.2143	$11.21	$11.20	$11.20
Purchase #4	$179.28	3.277%	$185.155	$185.16	$185.15	$185.20
Purchase #5	$158.28	8.498%	$171.7306	$171.73	$171.75	$171.70
Purchase #6	$64.52	12.599%	$72.6489	$72.65	$72.65	$72.60
Purchase #7	$107.35	10.728%	$118.8665	$118.87	$118.85	$118.90
7 purchase totals =	$651.62		$702.0075	$702.01	$702.00	$702.00