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	$128.98	11.474%	$143.7792	$143.78	$143.80	$143.80
Purchase #2	$76.47	11.317%	$85.1241	$85.12	$85.10	$85.10
Purchase #3	$93.46	12.505%	$105.1472	$105.15	$105.15	$105.10
Purchase #4	$151.81	9.369%	$166.0331	$166.03	$166.05	$166.00
Purchase #5	$244.52	11.149%	$271.7815	$271.78	$271.80	$271.80
Purchase #6	$89.71	6.431%	$95.4793	$95.48	$95.50	$95.50
Purchase #7	$91.37	6.421%	$97.2369	$97.24	$97.25	$97.20
7 purchase totals =	$876.32		$964.5813	$964.58	$964.65	$964.50