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	$150.56	13.650%	$171.1114	$171.11	$171.10	$171.10
Purchase #2	$35.62	13.611%	$40.4682	$40.47	$40.45	$40.50
Purchase #3	$223.38	7.866%	$240.9511	$240.95	$240.95	$241.00
Purchase #4	$109.70	5.781%	$116.0418	$116.04	$116.05	$116.00
Purchase #5	$175.62	6.667%	$187.3286	$187.33	$187.35	$187.30
Purchase #6	$228.35	10.277%	$251.8175	$251.82	$251.80	$251.80
Purchase #7	$146.92	5.232%	$154.6069	$154.61	$154.60	$154.60
7 purchase totals =	$1,070.15		$1,162.3255	$1,162.33	$1,162.30	$1,162.30