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	$22.75	3.762%	$23.6059	$23.61	$23.60	$23.60
Purchase #2	$239.67	7.760%	$258.2684	$258.27	$258.25	$258.30
Purchase #3	$198.31	5.342%	$208.9037	$208.90	$208.90	$208.90
Purchase #4	$90.57	12.714%	$102.0851	$102.09	$102.10	$102.10
Purchase #5	$96.57	3.344%	$99.7993	$99.80	$99.80	$99.80
Purchase #6	$113.99	5.748%	$120.5421	$120.54	$120.55	$120.50
Purchase #7	$188.74	9.320%	$206.3306	$206.33	$206.35	$206.30
7 purchase totals =	$950.60		$1,019.5351	$1,019.54	$1,019.55	$1,019.50