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	$238.65	4.621%	$249.678	$249.68	$249.70	$249.70
Purchase #2	$129.30	9.207%	$141.2047	$141.20	$141.20	$141.20
Purchase #3	$192.32	12.574%	$216.5023	$216.50	$216.50	$216.50
Purchase #4	$127.89	9.799%	$140.4219	$140.42	$140.40	$140.40
Purchase #5	$93.58	7.373%	$100.4797	$100.48	$100.50	$100.50
Purchase #6	$89.98	6.238%	$95.593	$95.59	$95.60	$95.60
Purchase #7	$181.70	4.736%	$190.3053	$190.31	$190.30	$190.30
7 purchase totals =	$1,053.42		$1,134.1849	$1,134.18	$1,134.20	$1,134.20