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	$84.36	7.449%	$90.644	$90.64	$90.65	$90.60
Purchase #2	$82.49	7.664%	$88.812	$88.81	$88.80	$88.80
Purchase #3	$120.31	5.673%	$127.1352	$127.14	$127.15	$127.10
Purchase #4	$200.38	6.629%	$213.6632	$213.66	$213.65	$213.70
Purchase #5	$90.76	6.289%	$96.4679	$96.47	$96.45	$96.50
Purchase #6	$14.81	13.547%	$16.8163	$16.82	$16.80	$16.80
Purchase #7	$174.71	10.476%	$193.0126	$193.01	$193.00	$193.00
7 purchase totals =	$767.82		$826.5512	$826.55	$826.50	$826.50