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	$7.51	5.730%	$7.9403	$7.94	$7.95	$7.90
Purchase #2	$39.39	9.630%	$43.1833	$43.18	$43.20	$43.20
Purchase #3	$68.27	12.610%	$76.8788	$76.88	$76.90	$76.90
Purchase #4	$116.78	9.510%	$127.8858	$127.89	$127.90	$127.90
Purchase #5	$243.57	9.859%	$267.5836	$267.58	$267.60	$267.60
Purchase #6	$227.66	11.529%	$253.9069	$253.91	$253.90	$253.90
Purchase #7	$48.80	5.263%	$51.3683	$51.37	$51.35	$51.40
7 purchase totals =	$751.98		$828.7470	$828.75	$828.80	$828.80