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	$107.56	4.264%	$112.1464	$112.15	$112.15	$112.10
Purchase #2	$18.73	6.441%	$19.9364	$19.94	$19.95	$19.90
Purchase #3	$214.51	9.583%	$235.0665	$235.07	$235.05	$235.10
Purchase #4	$123.97	13.190%	$140.3216	$140.32	$140.30	$140.30
Purchase #5	$240.71	13.190%	$272.4596	$272.46	$272.45	$272.50
Purchase #6	$84.33	10.767%	$93.4098	$93.41	$93.40	$93.40
Purchase #7	$203.34	9.614%	$222.8891	$222.89	$222.90	$222.90
7 purchase totals =	$993.15		$1,096.2294	$1,096.24	$1,096.20	$1,096.20