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	$162.73	7.188%	$174.427	$174.43	$174.45	$174.40
Purchase #2	$127.47	12.786%	$143.7683	$143.77	$143.75	$143.80
Purchase #3	$51.85	3.720%	$53.7788	$53.78	$53.80	$53.80
Purchase #4	$109.43	3.436%	$113.19	$113.19	$113.20	$113.20
Purchase #5	$39.53	4.141%	$41.1669	$41.17	$41.15	$41.20
Purchase #6	$113.81	10.268%	$125.496	$125.50	$125.50	$125.50
Purchase #7	$80.53	11.473%	$89.7692	$89.77	$89.75	$89.80
7 purchase totals =	$685.35		$741.5962	$741.61	$741.60	$741.70