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	$36.68	4.845%	$38.4571	$38.46	$38.45	$38.50
Purchase #2	$115.26	13.542%	$130.8685	$130.87	$130.85	$130.90
Purchase #3	$73.85	12.575%	$83.1366	$83.14	$83.15	$83.10
Purchase #4	$198.59	3.258%	$205.0601	$205.06	$205.05	$205.10
Purchase #5	$206.77	12.704%	$233.0381	$233.04	$233.05	$233.00
Purchase #6	$53.32	3.448%	$55.1585	$55.16	$55.15	$55.20
Purchase #7	$237.69	12.342%	$267.0257	$267.03	$267.05	$267.00
7 purchase totals =	$922.16		$1,012.7446	$1,012.76	$1,012.75	$1,012.80