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	$69.25	13.451%	$78.5648	$78.56	$78.55	$78.60
Purchase #2	$164.59	13.781%	$187.2721	$187.27	$187.25	$187.30
Purchase #3	$27.28	13.570%	$30.9819	$30.98	$31.00	$31.00
Purchase #4	$111.63	13.195%	$126.3596	$126.36	$126.35	$126.40
Purchase #5	$140.55	4.687%	$147.1376	$147.14	$147.15	$147.10
Purchase #6	$58.29	12.414%	$65.5261	$65.53	$65.55	$65.50
Purchase #7	$70.69	11.601%	$78.8907	$78.89	$78.90	$78.90
7 purchase totals =	$642.28		$714.7328	$714.73	$714.75	$714.80