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	$56.48	12.475%	$63.5259	$63.53	$63.55	$63.50
Purchase #2	$78.51	5.616%	$82.9191	$82.92	$82.90	$82.90
Purchase #3	$235.36	4.229%	$245.3134	$245.31	$245.30	$245.30
Purchase #4	$17.36	8.653%	$18.8622	$18.86	$18.85	$18.90
Purchase #5	$170.59	12.250%	$191.4873	$191.49	$191.50	$191.50
Purchase #6	$155.51	4.560%	$162.6013	$162.60	$162.60	$162.60
Purchase #7	$232.25	3.861%	$241.2172	$241.22	$241.20	$241.20
7 purchase totals =	$946.06		$1,005.9264	$1,005.93	$1,005.90	$1,005.90