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	$118.74	7.639%	$127.8105	$127.81	$127.80	$127.80
Purchase #2	$37.58	12.200%	$42.1648	$42.16	$42.15	$42.20
Purchase #3	$39.36	3.535%	$40.7514	$40.75	$40.75	$40.80
Purchase #4	$211.77	4.332%	$220.9439	$220.94	$220.95	$220.90
Purchase #5	$222.91	4.742%	$233.4804	$233.48	$233.50	$233.50
Purchase #6	$178.33	7.867%	$192.3592	$192.36	$192.35	$192.40
Purchase #7	$65.46	10.716%	$72.4747	$72.47	$72.45	$72.50
7 purchase totals =	$874.15		$929.9849	$929.97	$929.95	$930.10