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	$43.78	10.426%	$48.3445	$48.34	$48.35	$48.30
Purchase #2	$57.88	5.608%	$61.1259	$61.13	$61.15	$61.10
Purchase #3	$30.25	6.201%	$32.1258	$32.13	$32.15	$32.10
Purchase #4	$6.51	4.419%	$6.7977	$6.80	$6.80	$6.80
Purchase #5	$165.93	4.556%	$173.4898	$173.49	$173.50	$173.50
Purchase #6	$117.84	4.649%	$123.3184	$123.32	$123.30	$123.30
Purchase #7	$227.47	12.847%	$256.6931	$256.69	$256.70	$256.70
7 purchase totals =	$649.66		$701.8952	$701.90	$701.95	$701.80