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	$102.62	6.837%	$109.6361	$109.64	$109.65	$109.60
Purchase #2	$25.74	12.189%	$28.8774	$28.88	$28.90	$28.90
Purchase #3	$85.29	3.231%	$88.0457	$88.05	$88.05	$88.00
Purchase #4	$125.73	11.808%	$140.5762	$140.58	$140.60	$140.60
Purchase #5	$81.79	11.830%	$91.4658	$91.47	$91.45	$91.50
Purchase #6	$83.35	3.796%	$86.514	$86.51	$86.50	$86.50
Purchase #7	$170.25	11.374%	$189.6142	$189.61	$189.60	$189.60
7 purchase totals =	$674.77		$734.7294	$734.74	$734.75	$734.70