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	$69.66	4.493%	$72.7898	$72.79	$72.80	$72.80
Purchase #2	$133.64	9.367%	$146.1581	$146.16	$146.15	$146.20
Purchase #3	$200.34	5.580%	$211.519	$211.52	$211.50	$211.50
Purchase #4	$112.89	12.565%	$127.0746	$127.07	$127.05	$127.10
Purchase #5	$131.69	7.267%	$141.2599	$141.26	$141.25	$141.30
Purchase #6	$168.48	6.517%	$179.4598	$179.46	$179.45	$179.50
Purchase #7	$175.89	6.209%	$186.811	$186.81	$186.80	$186.80
7 purchase totals =	$992.59		$1,065.0722	$1,065.07	$1,065.00	$1,065.20