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	$236.67	12.788%	$266.9354	$266.94	$266.95	$266.90
Purchase #2	$240.83	6.172%	$255.694	$255.69	$255.70	$255.70
Purchase #3	$220.51	4.810%	$231.1165	$231.12	$231.10	$231.10
Purchase #4	$210.28	8.701%	$228.5765	$228.58	$228.60	$228.60
Purchase #5	$209.67	13.870%	$238.7512	$238.75	$238.75	$238.80
Purchase #6	$183.76	4.655%	$192.314	$192.31	$192.30	$192.30
Purchase #7	$186.33	5.654%	$196.8651	$196.87	$196.85	$196.90
7 purchase totals =	$1,488.05		$1,610.2527	$1,610.26	$1,610.25	$1,610.30