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	$224.81	9.409%	$245.9624	$245.96	$245.95	$246.00
Purchase #2	$111.81	10.709%	$123.7837	$123.78	$123.80	$123.80
Purchase #3	$129.77	12.761%	$146.3299	$146.33	$146.35	$146.30
Purchase #4	$120.63	3.288%	$124.5963	$124.60	$124.60	$124.60
Purchase #5	$152.60	7.499%	$164.0435	$164.04	$164.05	$164.00
Purchase #6	$59.33	6.669%	$63.2867	$63.29	$63.30	$63.30
Purchase #7	$184.86	4.697%	$193.5429	$193.54	$193.55	$193.50
7 purchase totals =	$983.81		$1,061.5454	$1,061.54	$1,061.60	$1,061.50