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	$249.39	5.419%	$262.9044	$262.90	$262.90	$262.90
Purchase #2	$58.88	11.173%	$65.4587	$65.46	$65.45	$65.50
Purchase #3	$112.98	13.607%	$128.3532	$128.35	$128.35	$128.40
Purchase #4	$37.93	6.189%	$40.2775	$40.28	$40.30	$40.30
Purchase #5	$192.50	7.119%	$206.2041	$206.20	$206.20	$206.20
Purchase #6	$234.83	6.122%	$249.2063	$249.21	$249.20	$249.20
Purchase #7	$62.56	6.511%	$66.6333	$66.63	$66.65	$66.60
7 purchase totals =	$949.07		$1,019.0375	$1,019.03	$1,019.05	$1,019.10