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	$117.67	8.574%	$127.759	$127.76	$127.75	$127.80
Purchase #2	$102.36	10.695%	$113.3074	$113.31	$113.30	$113.30
Purchase #3	$82.80	9.367%	$90.5559	$90.56	$90.55	$90.60
Purchase #4	$99.25	10.608%	$109.7784	$109.78	$109.80	$109.80
Purchase #5	$59.63	12.377%	$67.0104	$67.01	$67.00	$67.00
Purchase #6	$196.31	5.692%	$207.484	$207.48	$207.50	$207.50
Purchase #7	$212.70	5.418%	$224.2241	$224.22	$224.20	$224.20
7 purchase totals =	$870.72		$940.1192	$940.12	$940.10	$940.20