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	$169.57	6.253%	$180.1732	$180.17	$180.15	$180.20
Purchase #2	$27.91	12.696%	$31.4535	$31.45	$31.45	$31.50
Purchase #3	$59.69	8.153%	$64.5565	$64.56	$64.55	$64.60
Purchase #4	$233.61	3.832%	$242.5619	$242.56	$242.55	$242.60
Purchase #5	$77.75	12.448%	$87.4283	$87.43	$87.45	$87.40
Purchase #6	$96.29	4.742%	$100.8561	$100.86	$100.85	$100.90
Purchase #7	$83.67	6.294%	$88.9362	$88.94	$88.95	$88.90
7 purchase totals =	$748.49		$795.9657	$795.97	$795.95	$796.10