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	$123.78	5.777%	$130.9308	$130.93	$130.95	$130.90
Purchase #2	$183.44	13.489%	$208.1842	$208.18	$208.20	$208.20
Purchase #3	$43.51	3.170%	$44.8893	$44.89	$44.90	$44.90
Purchase #4	$48.37	11.350%	$53.86	$53.86	$53.85	$53.90
Purchase #5	$88.67	10.792%	$98.2393	$98.24	$98.25	$98.20
Purchase #6	$241.42	12.109%	$270.6535	$270.65	$270.65	$270.70
Purchase #7	$55.72	11.481%	$62.1172	$62.12	$62.10	$62.10
7 purchase totals =	$784.91		$868.8743	$868.87	$868.90	$868.90