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	$130.60	10.676%	$144.5429	$144.54	$144.55	$144.50
Purchase #2	$103.68	7.486%	$111.4415	$111.44	$111.45	$111.40
Purchase #3	$71.53	13.445%	$81.1472	$81.15	$81.15	$81.10
Purchase #4	$34.69	4.152%	$36.1303	$36.13	$36.15	$36.10
Purchase #5	$203.69	13.452%	$231.0904	$231.09	$231.10	$231.10
Purchase #6	$100.93	9.278%	$110.2943	$110.29	$110.30	$110.30
Purchase #7	$95.88	5.735%	$101.3787	$101.38	$101.40	$101.40
7 purchase totals =	$741.00		$816.0253	$816.02	$816.10	$815.90