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	$148.77	13.542%	$168.9164	$168.92	$168.90	$168.90
Purchase #2	$197.44	10.639%	$218.4456	$218.45	$218.45	$218.40
Purchase #3	$147.42	9.153%	$160.9134	$160.91	$160.90	$160.90
Purchase #4	$219.26	12.400%	$246.4482	$246.45	$246.45	$246.40
Purchase #5	$104.59	11.415%	$116.5289	$116.53	$116.55	$116.50
Purchase #6	$51.39	8.355%	$55.6836	$55.68	$55.70	$55.70
Purchase #7	$130.51	10.388%	$144.0674	$144.07	$144.05	$144.10
7 purchase totals =	$999.38		$1,111.0035	$1,111.01	$1,111.00	$1,110.90