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	$172.64	4.520%	$180.4433	$180.44	$180.45	$180.40
Purchase #2	$238.98	9.654%	$262.0511	$262.05	$262.05	$262.10
Purchase #3	$212.39	4.695%	$222.3617	$222.36	$222.35	$222.40
Purchase #4	$95.77	6.832%	$102.313	$102.31	$102.30	$102.30
Purchase #5	$153.59	3.336%	$158.7138	$158.71	$158.70	$158.70
Purchase #6	$64.75	4.226%	$67.4863	$67.49	$67.50	$67.50
Purchase #7	$116.86	5.294%	$123.0466	$123.05	$123.05	$123.00
7 purchase totals =	$1,054.98		$1,116.4158	$1,116.41	$1,116.40	$1,116.40