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	$131.73	7.829%	$142.0431	$142.04	$142.05	$142.00
Purchase #2	$109.54	13.140%	$123.9336	$123.93	$123.95	$123.90
Purchase #3	$87.96	4.324%	$91.7634	$91.76	$91.75	$91.80
Purchase #4	$202.42	3.177%	$208.8509	$208.85	$208.85	$208.90
Purchase #5	$223.44	11.673%	$249.5222	$249.52	$249.50	$249.50
Purchase #6	$81.65	4.246%	$85.1169	$85.12	$85.10	$85.10
Purchase #7	$147.70	8.845%	$160.7641	$160.76	$160.75	$160.80
7 purchase totals =	$984.44		$1,061.9942	$1,061.98	$1,061.95	$1,062.00