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	$221.73	13.607%	$251.9008	$251.90	$251.90	$251.90
Purchase #2	$166.32	11.805%	$185.9541	$185.95	$185.95	$186.00
Purchase #3	$53.93	10.734%	$59.7188	$59.72	$59.70	$59.70
Purchase #4	$116.43	6.636%	$124.1563	$124.16	$124.15	$124.20
Purchase #5	$64.91	13.867%	$73.9111	$73.91	$73.90	$73.90
Purchase #6	$183.51	13.758%	$208.7573	$208.76	$208.75	$208.80
Purchase #7	$171.89	8.713%	$186.8668	$186.87	$186.85	$186.90
7 purchase totals =	$978.72		$1,091.2652	$1,091.27	$1,091.20	$1,091.40