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	$79.46	4.851%	$83.3146	$83.31	$83.30	$83.30
Purchase #2	$72.54	10.746%	$80.3351	$80.34	$80.35	$80.30
Purchase #3	$181.96	13.239%	$206.0497	$206.05	$206.05	$206.00
Purchase #4	$139.65	13.706%	$158.7904	$158.79	$158.80	$158.80
Purchase #5	$200.93	12.102%	$225.2465	$225.25	$225.25	$225.20
Purchase #6	$94.60	4.730%	$99.0746	$99.07	$99.05	$99.10
Purchase #7	$152.76	12.374%	$171.6625	$171.66	$171.65	$171.70
7 purchase totals =	$921.90		$1,024.4734	$1,024.47	$1,024.45	$1,024.40