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	$150.66	11.743%	$168.352	$168.35	$168.35	$168.40
Purchase #2	$236.59	5.449%	$249.4818	$249.48	$249.50	$249.50
Purchase #3	$182.95	9.652%	$200.6083	$200.61	$200.60	$200.60
Purchase #4	$41.58	10.874%	$46.1014	$46.10	$46.10	$46.10
Purchase #5	$92.96	6.572%	$99.0693	$99.07	$99.05	$99.10
Purchase #6	$28.73	12.214%	$32.2391	$32.24	$32.25	$32.20
Purchase #7	$47.34	8.721%	$51.4685	$51.47	$51.45	$51.50
7 purchase totals =	$780.81		$847.3204	$847.32	$847.30	$847.40