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	$22.35	10.219%	$24.6339	$24.63	$24.65	$24.60
Purchase #2	$215.90	4.596%	$225.8228	$225.82	$225.80	$225.80
Purchase #3	$201.34	10.506%	$222.4928	$222.49	$222.50	$222.50
Purchase #4	$45.32	4.372%	$47.3014	$47.30	$47.30	$47.30
Purchase #5	$223.48	6.304%	$237.5682	$237.57	$237.55	$237.60
Purchase #6	$102.72	8.347%	$111.294	$111.29	$111.30	$111.30
Purchase #7	$159.82	4.124%	$166.411	$166.41	$166.40	$166.40
7 purchase totals =	$970.93		$1,035.5241	$1,035.51	$1,035.50	$1,035.50