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	$173.90	10.368%	$191.93	$191.93	$191.95	$191.90
Purchase #2	$13.94	9.802%	$15.3064	$15.31	$15.30	$15.30
Purchase #3	$221.63	5.806%	$234.4978	$234.50	$234.50	$234.50
Purchase #4	$106.28	3.573%	$110.0774	$110.08	$110.10	$110.10
Purchase #5	$79.50	13.131%	$89.9391	$89.94	$89.95	$89.90
Purchase #6	$110.38	12.108%	$123.7448	$123.74	$123.75	$123.70
Purchase #7	$117.80	7.627%	$126.7846	$126.78	$126.80	$126.80
7 purchase totals =	$823.43		$892.2801	$892.28	$892.35	$892.20