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	$184.99	6.763%	$197.5009	$197.50	$197.50	$197.50
Purchase #2	$207.46	8.536%	$225.1688	$225.17	$225.15	$225.20
Purchase #3	$144.38	5.837%	$152.8075	$152.81	$152.80	$152.80
Purchase #4	$170.96	13.477%	$194.0003	$194.00	$194.00	$194.00
Purchase #5	$40.72	3.686%	$42.2209	$42.22	$42.20	$42.20
Purchase #6	$185.45	3.313%	$191.594	$191.59	$191.60	$191.60
Purchase #7	$103.38	5.759%	$109.3337	$109.33	$109.35	$109.30
7 purchase totals =	$1,037.34		$1,112.6261	$1,112.62	$1,112.60	$1,112.60