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	$205.25	12.494%	$230.8939	$230.89	$230.90	$230.90
Purchase #2	$212.94	7.719%	$229.3768	$229.38	$229.40	$229.40
Purchase #3	$185.84	3.431%	$192.2162	$192.22	$192.20	$192.20
Purchase #4	$109.91	12.539%	$123.6916	$123.69	$123.70	$123.70
Purchase #5	$46.25	4.121%	$48.156	$48.16	$48.15	$48.20
Purchase #6	$183.90	3.476%	$190.2924	$190.29	$190.30	$190.30
Purchase #7	$49.46	5.488%	$52.1744	$52.17	$52.15	$52.20
7 purchase totals =	$993.55		$1,066.8013	$1,066.80	$1,066.80	$1,066.90