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	$233.30	12.507%	$262.4788	$262.48	$262.50	$262.50
Purchase #2	$33.44	8.419%	$36.2553	$36.26	$36.25	$36.30
Purchase #3	$65.27	12.261%	$73.2728	$73.27	$73.25	$73.30
Purchase #4	$77.73	8.138%	$84.0557	$84.06	$84.05	$84.10
Purchase #5	$54.55	5.221%	$57.3981	$57.40	$57.40	$57.40
Purchase #6	$56.57	4.487%	$59.1083	$59.11	$59.10	$59.10
Purchase #7	$119.45	7.124%	$127.9596	$127.96	$127.95	$128.00
7 purchase totals =	$640.31		$700.5286	$700.54	$700.50	$700.70