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	$92.83	10.771%	$102.8287	$102.83	$102.85	$102.80
Purchase #2	$144.86	4.649%	$151.5945	$151.59	$151.60	$151.60
Purchase #3	$224.69	10.429%	$248.1229	$248.12	$248.10	$248.10
Purchase #4	$130.73	5.778%	$138.2836	$138.28	$138.30	$138.30
Purchase #5	$60.59	13.233%	$68.6079	$68.61	$68.60	$68.60
Purchase #6	$28.95	11.143%	$32.1759	$32.18	$32.20	$32.20
Purchase #7	$250.48	9.315%	$273.8122	$273.81	$273.80	$273.80
7 purchase totals =	$933.13		$1,015.4257	$1,015.42	$1,015.45	$1,015.40