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	$117.72	4.609%	$123.1457	$123.15	$123.15	$123.10
Purchase #2	$153.78	11.702%	$171.7753	$171.78	$171.80	$171.80
Purchase #3	$170.30	13.306%	$192.9601	$192.96	$192.95	$193.00
Purchase #4	$212.92	11.836%	$238.1212	$238.12	$238.10	$238.10
Purchase #5	$95.76	10.326%	$105.6482	$105.65	$105.65	$105.60
Purchase #6	$159.46	9.124%	$174.0091	$174.01	$174.00	$174.00
Purchase #7	$190.92	9.567%	$209.1853	$209.19	$209.20	$209.20
7 purchase totals =	$1,100.86		$1,214.8449	$1,214.86	$1,214.85	$1,214.80