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	$209.80	8.514%	$227.6624	$227.66	$227.65	$227.70
Purchase #2	$53.26	12.571%	$59.9553	$59.96	$59.95	$60.00
Purchase #3	$187.35	10.496%	$207.0143	$207.01	$207.00	$207.00
Purchase #4	$143.37	6.643%	$152.8941	$152.89	$152.90	$152.90
Purchase #5	$37.91	13.717%	$43.1101	$43.11	$43.10	$43.10
Purchase #6	$75.90	12.511%	$85.3958	$85.40	$85.40	$85.40
Purchase #7	$84.63	6.626%	$90.2376	$90.24	$90.25	$90.20
7 purchase totals =	$792.22		$866.2696	$866.27	$866.25	$866.30