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	$68.45	5.289%	$72.0703	$72.07	$72.05	$72.10
Purchase #2	$111.65	5.812%	$118.1391	$118.14	$118.15	$118.10
Purchase #3	$192.86	10.586%	$213.2762	$213.28	$213.30	$213.30
Purchase #4	$192.43	13.561%	$218.5254	$218.53	$218.55	$218.50
Purchase #5	$192.48	8.543%	$208.9236	$208.92	$208.90	$208.90
Purchase #6	$36.97	12.854%	$41.7221	$41.72	$41.70	$41.70
Purchase #7	$95.88	5.146%	$100.814	$100.81	$100.80	$100.80
7 purchase totals =	$890.72		$973.4707	$973.47	$973.45	$973.40