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	$47.47	12.424%	$53.3677	$53.37	$53.35	$53.40
Purchase #2	$187.47	9.427%	$205.1428	$205.14	$205.15	$205.10
Purchase #3	$147.89	5.747%	$156.3892	$156.39	$156.40	$156.40
Purchase #4	$38.55	11.477%	$42.9744	$42.97	$42.95	$43.00
Purchase #5	$153.92	4.274%	$160.4985	$160.50	$160.50	$160.50
Purchase #6	$140.28	4.148%	$146.0988	$146.10	$146.10	$146.10
Purchase #7	$51.82	11.857%	$57.9643	$57.96	$57.95	$58.00
7 purchase totals =	$767.40		$822.4357	$822.43	$822.40	$822.50