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	$142.86	11.489%	$159.2732	$159.27	$159.25	$159.30
Purchase #2	$243.98	8.739%	$265.3014	$265.30	$265.30	$265.30
Purchase #3	$10.67	8.328%	$11.5586	$11.56	$11.55	$11.60
Purchase #4	$176.54	12.637%	$198.8494	$198.85	$198.85	$198.80
Purchase #5	$75.84	12.414%	$85.2548	$85.25	$85.25	$85.30
Purchase #6	$40.50	9.789%	$44.4645	$44.46	$44.45	$44.50
Purchase #7	$235.33	3.709%	$244.0584	$244.06	$244.05	$244.10
7 purchase totals =	$925.72		$1,008.7603	$1,008.75	$1,008.70	$1,008.90