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	$191.51	3.712%	$198.6189	$198.62	$198.60	$198.60
Purchase #2	$95.44	3.310%	$98.5991	$98.60	$98.60	$98.60
Purchase #3	$242.38	6.667%	$258.5395	$258.54	$258.55	$258.50
Purchase #4	$87.81	4.172%	$91.4734	$91.47	$91.45	$91.50
Purchase #5	$245.79	7.186%	$263.4525	$263.45	$263.45	$263.50
Purchase #6	$37.72	9.106%	$41.1548	$41.15	$41.15	$41.20
Purchase #7	$228.60	12.137%	$256.3452	$256.35	$256.35	$256.30
7 purchase totals =	$1,129.25		$1,208.1834	$1,208.18	$1,208.15	$1,208.20