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	$221.69	4.279%	$231.1761	$231.18	$231.20	$231.20
Purchase #2	$70.89	4.222%	$73.883	$73.88	$73.90	$73.90
Purchase #3	$29.38	4.808%	$30.7926	$30.79	$30.80	$30.80
Purchase #4	$97.54	8.248%	$105.5851	$105.59	$105.60	$105.60
Purchase #5	$55.88	7.193%	$59.8994	$59.90	$59.90	$59.90
Purchase #6	$201.91	5.431%	$212.8757	$212.88	$212.90	$212.90
Purchase #7	$38.76	13.354%	$43.936	$43.94	$43.95	$43.90
7 purchase totals =	$716.05		$758.1479	$758.16	$758.25	$758.20