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	$6.88	6.437%	$7.3229	$7.32	$7.30	$7.30
Purchase #2	$75.82	12.542%	$85.3293	$85.33	$85.35	$85.30
Purchase #3	$219.26	4.260%	$228.6005	$228.60	$228.60	$228.60
Purchase #4	$235.78	11.419%	$262.7037	$262.70	$262.70	$262.70
Purchase #5	$240.89	10.661%	$266.5713	$266.57	$266.55	$266.60
Purchase #6	$57.63	13.638%	$65.4896	$65.49	$65.50	$65.50
Purchase #7	$150.80	12.273%	$169.3077	$169.31	$169.30	$169.30
7 purchase totals =	$987.06		$1,085.3250	$1,085.32	$1,085.30	$1,085.30