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	$184.32	3.388%	$190.5648	$190.56	$190.55	$190.60
Purchase #2	$36.97	12.134%	$41.4559	$41.46	$41.45	$41.50
Purchase #3	$145.61	4.119%	$151.6077	$151.61	$151.60	$151.60
Purchase #4	$249.70	8.474%	$270.8596	$270.86	$270.85	$270.90
Purchase #5	$192.62	6.663%	$205.4543	$205.45	$205.45	$205.50
Purchase #6	$27.45	13.794%	$31.2365	$31.24	$31.25	$31.20
Purchase #7	$167.88	13.372%	$190.3289	$190.33	$190.35	$190.30
7 purchase totals =	$1,004.55		$1,081.5077	$1,081.51	$1,081.50	$1,081.60