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	$57.78	9.523%	$63.2824	$63.28	$63.30	$63.30
Purchase #2	$137.70	4.808%	$144.3206	$144.32	$144.30	$144.30
Purchase #3	$145.32	3.464%	$150.3539	$150.35	$150.35	$150.40
Purchase #4	$27.80	6.268%	$29.5425	$29.54	$29.55	$29.50
Purchase #5	$19.36	13.122%	$21.9004	$21.90	$21.90	$21.90
Purchase #6	$25.69	6.707%	$27.413	$27.41	$27.40	$27.40
Purchase #7	$56.36	8.777%	$61.3067	$61.31	$61.30	$61.30
7 purchase totals =	$470.01		$498.1195	$498.11	$498.10	$498.10