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	$112.92	3.225%	$116.5617	$116.56	$116.55	$116.60
Purchase #2	$143.64	9.685%	$157.5515	$157.55	$157.55	$157.60
Purchase #3	$31.60	12.807%	$35.647	$35.65	$35.65	$35.60
Purchase #4	$10.52	9.125%	$11.48	$11.48	$11.50	$11.50
Purchase #5	$95.52	6.280%	$101.5187	$101.52	$101.50	$101.50
Purchase #6	$54.38	6.350%	$57.8331	$57.83	$57.85	$57.80
Purchase #7	$178.93	5.718%	$189.1612	$189.16	$189.15	$189.20
7 purchase totals =	$627.51		$669.7532	$669.75	$669.75	$669.80