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	$238.28	11.170%	$264.8959	$264.90	$264.90	$264.90
Purchase #2	$76.87	9.145%	$83.8998	$83.90	$83.90	$83.90
Purchase #3	$214.86	6.801%	$229.4726	$229.47	$229.45	$229.50
Purchase #4	$27.48	7.343%	$29.4979	$29.50	$29.50	$29.50
Purchase #5	$159.30	10.473%	$175.9835	$175.98	$176.00	$176.00
Purchase #6	$5.59	13.368%	$6.3373	$6.34	$6.35	$6.30
Purchase #7	$244.47	5.863%	$258.8033	$258.80	$258.80	$258.80
7 purchase totals =	$966.85		$1,048.8903	$1,048.89	$1,048.90	$1,048.90