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	$153.69	3.385%	$158.8924	$158.89	$158.90	$158.90
Purchase #2	$150.91	13.386%	$171.1108	$171.11	$171.10	$171.10
Purchase #3	$149.91	9.613%	$164.3208	$164.32	$164.30	$164.30
Purchase #4	$117.48	8.621%	$127.608	$127.61	$127.60	$127.60
Purchase #5	$99.66	12.744%	$112.3607	$112.36	$112.35	$112.40
Purchase #6	$72.30	5.373%	$76.1847	$76.18	$76.20	$76.20
Purchase #7	$51.67	12.176%	$57.9613	$57.96	$57.95	$58.00
7 purchase totals =	$795.62		$868.4387	$868.43	$868.40	$868.50