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	$236.90	12.787%	$267.1924	$267.19	$267.20	$267.20
Purchase #2	$74.27	5.464%	$78.3281	$78.33	$78.35	$78.30
Purchase #3	$161.56	5.125%	$169.84	$169.84	$169.85	$169.80
Purchase #4	$242.29	7.499%	$260.4593	$260.46	$260.45	$260.50
Purchase #5	$121.71	7.656%	$131.0281	$131.03	$131.05	$131.00
Purchase #6	$81.86	7.218%	$87.7687	$87.77	$87.75	$87.80
Purchase #7	$52.56	13.339%	$59.571	$59.57	$59.55	$59.60
7 purchase totals =	$971.15		$1,054.1876	$1,054.19	$1,054.20	$1,054.20