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	$9.88	10.647%	$10.9319	$10.93	$10.95	$10.90
Purchase #2	$74.41	10.516%	$82.235	$82.24	$82.25	$82.20
Purchase #3	$139.96	5.710%	$147.9517	$147.95	$147.95	$148.00
Purchase #4	$178.59	10.243%	$196.883	$196.88	$196.90	$196.90
Purchase #5	$235.89	6.266%	$250.6709	$250.67	$250.65	$250.70
Purchase #6	$19.64	4.868%	$20.5961	$20.60	$20.60	$20.60
Purchase #7	$143.88	7.871%	$155.2048	$155.20	$155.20	$155.20
7 purchase totals =	$802.25		$864.4734	$864.47	$864.50	$864.50