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	$192.57	7.263%	$206.5564	$206.56	$206.55	$206.60
Purchase #2	$237.97	7.644%	$256.1604	$256.16	$256.15	$256.20
Purchase #3	$116.97	9.404%	$127.9699	$127.97	$127.95	$128.00
Purchase #4	$111.85	4.423%	$116.7971	$116.80	$116.80	$116.80
Purchase #5	$180.33	8.798%	$196.1954	$196.20	$196.20	$196.20
Purchase #6	$116.61	10.445%	$128.7899	$128.79	$128.80	$128.80
Purchase #7	$61.76	3.289%	$63.7913	$63.79	$63.80	$63.80
7 purchase totals =	$1,018.06		$1,096.2604	$1,096.27	$1,096.25	$1,096.40