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	$233.52	13.291%	$264.5571	$264.56	$264.55	$264.60
Purchase #2	$187.25	3.715%	$194.2063	$194.21	$194.20	$194.20
Purchase #3	$151.97	5.250%	$159.9484	$159.95	$159.95	$159.90
Purchase #4	$209.89	4.524%	$219.3854	$219.39	$219.40	$219.40
Purchase #5	$56.78	4.382%	$59.2681	$59.27	$59.25	$59.30
Purchase #6	$239.61	11.291%	$266.6644	$266.66	$266.65	$266.70
Purchase #7	$87.32	4.447%	$91.2031	$91.20	$91.20	$91.20
7 purchase totals =	$1,166.34		$1,255.2328	$1,255.24	$1,255.20	$1,255.30