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	$139.98	8.493%	$151.8685	$151.87	$151.85	$151.90
Purchase #2	$8.42	13.837%	$9.5851	$9.59	$9.60	$9.60
Purchase #3	$102.82	9.362%	$112.446	$112.45	$112.45	$112.40
Purchase #4	$202.80	3.361%	$209.6161	$209.62	$209.60	$209.60
Purchase #5	$130.40	6.675%	$139.1042	$139.10	$139.10	$139.10
Purchase #6	$38.81	8.114%	$41.959	$41.96	$41.95	$42.00
Purchase #7	$88.67	12.572%	$99.8176	$99.82	$99.80	$99.80
7 purchase totals =	$711.90		$764.3965	$764.41	$764.35	$764.40