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	$135.87	13.720%	$154.5114	$154.51	$154.50	$154.50
Purchase #2	$63.96	12.325%	$71.8431	$71.84	$71.85	$71.80
Purchase #3	$42.90	8.209%	$46.4217	$46.42	$46.40	$46.40
Purchase #4	$85.84	11.270%	$95.5142	$95.51	$95.50	$95.50
Purchase #5	$180.37	6.176%	$191.5097	$191.51	$191.50	$191.50
Purchase #6	$187.48	13.254%	$212.3286	$212.33	$212.35	$212.30
Purchase #7	$246.89	9.618%	$270.6359	$270.64	$270.65	$270.60
7 purchase totals =	$943.31		$1,042.7646	$1,042.76	$1,042.75	$1,042.60