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	$62.90	10.146%	$69.2818	$69.28	$69.30	$69.30
Purchase #2	$117.40	5.404%	$123.7443	$123.74	$123.75	$123.70
Purchase #3	$140.63	11.397%	$156.6576	$156.66	$156.65	$156.70
Purchase #4	$7.48	5.453%	$7.8879	$7.89	$7.90	$7.90
Purchase #5	$98.55	4.833%	$103.3129	$103.31	$103.30	$103.30
Purchase #6	$92.35	6.417%	$98.2761	$98.28	$98.30	$98.30
Purchase #7	$135.95	9.396%	$148.7239	$148.72	$148.70	$148.70
7 purchase totals =	$655.26		$707.8845	$707.88	$707.90	$707.90