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	$53.90	10.626%	$59.6274	$59.63	$59.65	$59.60
Purchase #2	$121.74	12.737%	$137.246	$137.25	$137.25	$137.20
Purchase #3	$203.91	3.263%	$210.5636	$210.56	$210.55	$210.60
Purchase #4	$182.61	3.380%	$188.7822	$188.78	$188.80	$188.80
Purchase #5	$70.55	11.549%	$78.6978	$78.70	$78.70	$78.70
Purchase #6	$223.31	4.199%	$232.6868	$232.69	$232.70	$232.70
Purchase #7	$106.46	5.868%	$112.7071	$112.71	$112.70	$112.70
7 purchase totals =	$962.48		$1,020.3109	$1,020.32	$1,020.35	$1,020.30