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	$235.94	12.450%	$265.3145	$265.31	$265.30	$265.30
Purchase #2	$242.79	7.710%	$261.5091	$261.51	$261.50	$261.50
Purchase #3	$229.45	10.673%	$253.9392	$253.94	$253.95	$253.90
Purchase #4	$151.90	11.214%	$168.9341	$168.93	$168.95	$168.90
Purchase #5	$211.91	11.426%	$236.1228	$236.12	$236.10	$236.10
Purchase #6	$89.83	7.407%	$96.4837	$96.48	$96.50	$96.50
Purchase #7	$142.43	13.244%	$161.2934	$161.29	$161.30	$161.30
7 purchase totals =	$1,304.25		$1,443.5968	$1,443.58	$1,443.60	$1,443.50