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	$234.78	11.221%	$261.1247	$261.12	$261.10	$261.10
Purchase #2	$95.97	5.815%	$101.5507	$101.55	$101.55	$101.60
Purchase #3	$145.56	3.409%	$150.5221	$150.52	$150.50	$150.50
Purchase #4	$31.61	4.570%	$33.0546	$33.05	$33.05	$33.10
Purchase #5	$246.75	8.492%	$267.704	$267.70	$267.70	$267.70
Purchase #6	$248.58	9.224%	$271.509	$271.51	$271.50	$271.50
Purchase #7	$33.40	12.845%	$37.6902	$37.69	$37.70	$37.70
7 purchase totals =	$1,036.65		$1,123.1553	$1,123.14	$1,123.10	$1,123.20