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	$163.67	6.568%	$174.4198	$174.42	$174.40	$174.40
Purchase #2	$167.80	10.394%	$185.2411	$185.24	$185.25	$185.20
Purchase #3	$186.48	5.320%	$196.4007	$196.40	$196.40	$196.40
Purchase #4	$138.52	4.389%	$144.5996	$144.60	$144.60	$144.60
Purchase #5	$233.70	11.728%	$261.1083	$261.11	$261.10	$261.10
Purchase #6	$204.77	3.645%	$212.2339	$212.23	$212.25	$212.20
Purchase #7	$131.64	7.428%	$141.4182	$141.42	$141.40	$141.40
7 purchase totals =	$1,226.58		$1,315.4216	$1,315.42	$1,315.40	$1,315.30