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	$143.64	4.369%	$149.9156	$149.92	$149.90	$149.90
Purchase #2	$108.94	11.481%	$121.4474	$121.45	$121.45	$121.40
Purchase #3	$89.43	12.357%	$100.4809	$100.48	$100.50	$100.50
Purchase #4	$146.55	5.344%	$154.3816	$154.38	$154.40	$154.40
Purchase #5	$58.78	7.845%	$63.3913	$63.39	$63.40	$63.40
Purchase #6	$240.36	10.304%	$265.1267	$265.13	$265.15	$265.10
Purchase #7	$124.76	13.437%	$141.524	$141.52	$141.50	$141.50
7 purchase totals =	$912.46		$996.2675	$996.27	$996.30	$996.20