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	$176.46	9.246%	$192.7755	$192.78	$192.80	$192.80
Purchase #2	$116.71	8.364%	$126.4716	$126.47	$126.45	$126.50
Purchase #3	$244.91	10.549%	$270.7456	$270.75	$270.75	$270.70
Purchase #4	$18.66	12.319%	$20.9587	$20.96	$20.95	$21.00
Purchase #5	$249.59	13.154%	$282.4211	$282.42	$282.40	$282.40
Purchase #6	$90.45	4.420%	$94.4479	$94.45	$94.45	$94.40
Purchase #7	$29.42	6.404%	$31.3041	$31.30	$31.30	$31.30
7 purchase totals =	$926.20		$1,019.1245	$1,019.13	$1,019.10	$1,019.10