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	$95.26	5.347%	$100.3536	$100.35	$100.35	$100.40
Purchase #2	$216.91	5.590%	$229.0353	$229.04	$229.05	$229.00
Purchase #3	$20.39	3.728%	$21.1501	$21.15	$21.15	$21.20
Purchase #4	$83.37	10.727%	$92.3131	$92.31	$92.30	$92.30
Purchase #5	$217.25	9.570%	$238.0408	$238.04	$238.05	$238.00
Purchase #6	$105.85	3.232%	$109.2711	$109.27	$109.25	$109.30
Purchase #7	$35.80	7.580%	$38.5136	$38.51	$38.50	$38.50
7 purchase totals =	$774.83		$828.6776	$828.67	$828.65	$828.70