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	$103.79	7.800%	$111.8856	$111.89	$111.90	$111.90
Purchase #2	$186.96	13.778%	$212.7193	$212.72	$212.70	$212.70
Purchase #3	$194.80	12.301%	$218.7623	$218.76	$218.75	$218.80
Purchase #4	$58.31	3.209%	$60.1812	$60.18	$60.20	$60.20
Purchase #5	$127.58	13.281%	$144.5239	$144.52	$144.50	$144.50
Purchase #6	$162.73	5.648%	$171.921	$171.92	$171.90	$171.90
Purchase #7	$87.67	8.487%	$95.1106	$95.11	$95.10	$95.10
7 purchase totals =	$921.84		$1,015.1039	$1,015.10	$1,015.05	$1,015.10