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	$200.85	4.234%	$209.354	$209.35	$209.35	$209.40
Purchase #2	$235.68	7.512%	$253.3843	$253.38	$253.40	$253.40
Purchase #3	$104.64	13.782%	$119.0615	$119.06	$119.05	$119.10
Purchase #4	$196.91	13.216%	$222.9336	$222.93	$222.95	$222.90
Purchase #5	$94.79	6.423%	$100.8784	$100.88	$100.90	$100.90
Purchase #6	$11.88	10.706%	$13.1519	$13.15	$13.15	$13.20
Purchase #7	$130.38	4.582%	$136.354	$136.35	$136.35	$136.40
7 purchase totals =	$975.13		$1,055.1177	$1,055.10	$1,055.15	$1,055.30