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	$56.41	7.281%	$60.5172	$60.52	$60.50	$60.50
Purchase #2	$11.98	13.338%	$13.5779	$13.58	$13.60	$13.60
Purchase #3	$65.27	13.151%	$73.8537	$73.85	$73.85	$73.90
Purchase #4	$84.53	4.227%	$88.1031	$88.10	$88.10	$88.10
Purchase #5	$6.76	5.440%	$7.1277	$7.13	$7.15	$7.10
Purchase #6	$89.31	13.536%	$101.399	$101.40	$101.40	$101.40
Purchase #7	$35.29	7.376%	$37.893	$37.89	$37.90	$37.90
7 purchase totals =	$349.55		$382.4716	$382.47	$382.50	$382.50