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	$143.45	7.652%	$154.4268	$154.43	$154.45	$154.40
Purchase #2	$41.89	3.737%	$43.4554	$43.46	$43.45	$43.50
Purchase #3	$108.34	3.430%	$112.0561	$112.06	$112.05	$112.10
Purchase #4	$209.30	5.696%	$221.2217	$221.22	$221.20	$221.20
Purchase #5	$69.37	4.745%	$72.6616	$72.66	$72.65	$72.70
Purchase #6	$49.31	6.341%	$52.4367	$52.44	$52.45	$52.40
Purchase #7	$121.83	11.689%	$136.0707	$136.07	$136.05	$136.10
7 purchase totals =	$743.49		$792.3290	$792.34	$792.30	$792.40