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	$134.47	6.265%	$142.8945	$142.89	$142.90	$142.90
Purchase #2	$186.33	12.452%	$209.5318	$209.53	$209.55	$209.50
Purchase #3	$221.86	9.824%	$243.6555	$243.66	$243.65	$243.70
Purchase #4	$65.93	10.628%	$72.937	$72.94	$72.95	$72.90
Purchase #5	$193.32	8.374%	$209.5086	$209.51	$209.50	$209.50
Purchase #6	$65.38	4.635%	$68.4104	$68.41	$68.40	$68.40
Purchase #7	$186.94	6.484%	$199.0612	$199.06	$199.05	$199.10
7 purchase totals =	$1,054.23		$1,145.9990	$1,146.00	$1,146.00	$1,146.00