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	$114.65	7.422%	$123.1593	$123.16	$123.15	$123.20
Purchase #2	$56.66	3.538%	$58.6646	$58.66	$58.65	$58.70
Purchase #3	$39.93	6.832%	$42.658	$42.66	$42.65	$42.70
Purchase #4	$27.49	6.654%	$29.3192	$29.32	$29.30	$29.30
Purchase #5	$50.52	9.416%	$55.277	$55.28	$55.30	$55.30
Purchase #6	$87.28	10.252%	$96.2279	$96.23	$96.25	$96.20
Purchase #7	$233.90	12.126%	$262.2627	$262.26	$262.25	$262.30
7 purchase totals =	$610.43		$667.5687	$667.57	$667.55	$667.70