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	$112.59	5.837%	$119.1619	$119.16	$119.15	$119.20
Purchase #2	$38.28	6.499%	$40.7678	$40.77	$40.75	$40.80
Purchase #3	$133.78	10.516%	$147.8483	$147.85	$147.85	$147.80
Purchase #4	$95.97	4.406%	$100.1984	$100.20	$100.20	$100.20
Purchase #5	$223.50	3.760%	$231.9036	$231.90	$231.90	$231.90
Purchase #6	$248.27	7.119%	$265.9443	$265.94	$265.95	$265.90
Purchase #7	$109.70	4.238%	$114.3491	$114.35	$114.35	$114.30
7 purchase totals =	$962.09		$1,020.1734	$1,020.17	$1,020.15	$1,020.10