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	$77.58	9.412%	$84.8818	$84.88	$84.90	$84.90
Purchase #2	$210.43	5.674%	$222.3698	$222.37	$222.35	$222.40
Purchase #3	$217.96	3.157%	$224.841	$224.84	$224.85	$224.80
Purchase #4	$87.98	12.870%	$99.303	$99.30	$99.30	$99.30
Purchase #5	$95.79	4.774%	$100.363	$100.36	$100.35	$100.40
Purchase #6	$165.61	3.338%	$171.1381	$171.14	$171.15	$171.10
Purchase #7	$55.71	11.762%	$62.2626	$62.26	$62.25	$62.30
7 purchase totals =	$911.06		$965.1593	$965.15	$965.15	$965.20