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	$183.33	7.252%	$196.6251	$196.63	$196.65	$196.60
Purchase #2	$80.83	5.449%	$85.2344	$85.23	$85.25	$85.20
Purchase #3	$234.93	6.287%	$249.7	$249.70	$249.70	$249.70
Purchase #4	$245.55	12.200%	$275.5071	$275.51	$275.50	$275.50
Purchase #5	$112.27	3.607%	$116.3196	$116.32	$116.30	$116.30
Purchase #6	$249.96	11.170%	$277.8805	$277.88	$277.90	$277.90
Purchase #7	$126.73	11.212%	$140.939	$140.94	$140.95	$140.90
7 purchase totals =	$1,233.60		$1,342.2057	$1,342.21	$1,342.25	$1,342.10