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	$130.71	11.400%	$145.6109	$145.61	$145.60	$145.60
Purchase #2	$63.39	3.188%	$65.4109	$65.41	$65.40	$65.40
Purchase #3	$102.66	8.767%	$111.6602	$111.66	$111.65	$111.70
Purchase #4	$188.38	3.140%	$194.2951	$194.30	$194.30	$194.30
Purchase #5	$76.27	12.529%	$85.8259	$85.83	$85.85	$85.80
Purchase #6	$191.76	12.583%	$215.8892	$215.89	$215.90	$215.90
Purchase #7	$184.31	4.313%	$192.2593	$192.26	$192.25	$192.30
7 purchase totals =	$937.48		$1,010.9515	$1,010.96	$1,010.95	$1,011.00