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	$184.25	11.848%	$206.0799	$206.08	$206.10	$206.10
Purchase #2	$81.37	10.844%	$90.1938	$90.19	$90.20	$90.20
Purchase #3	$35.78	10.185%	$39.4242	$39.42	$39.40	$39.40
Purchase #4	$52.34	6.539%	$55.7625	$55.76	$55.75	$55.80
Purchase #5	$87.63	7.221%	$93.9578	$93.96	$93.95	$94.00
Purchase #6	$68.46	4.360%	$71.4449	$71.44	$71.45	$71.40
Purchase #7	$182.50	4.401%	$190.5318	$190.53	$190.55	$190.50
7 purchase totals =	$692.33		$747.3949	$747.38	$747.40	$747.40