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	$225.59	10.304%	$248.8348	$248.83	$248.85	$248.80
Purchase #2	$153.60	10.242%	$169.3317	$169.33	$169.35	$169.30
Purchase #3	$89.73	12.510%	$100.9552	$100.96	$100.95	$101.00
Purchase #4	$154.98	3.270%	$160.0478	$160.05	$160.05	$160.00
Purchase #5	$239.61	5.801%	$253.5098	$253.51	$253.50	$253.50
Purchase #6	$122.87	3.809%	$127.5501	$127.55	$127.55	$127.60
Purchase #7	$227.70	12.471%	$256.0965	$256.10	$256.10	$256.10
7 purchase totals =	$1,214.08		$1,316.3259	$1,316.33	$1,316.35	$1,316.30