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	$13.39	5.745%	$14.1593	$14.16	$14.15	$14.20
Purchase #2	$123.65	11.721%	$138.143	$138.14	$138.15	$138.10
Purchase #3	$52.36	3.609%	$54.2497	$54.25	$54.25	$54.20
Purchase #4	$105.71	5.360%	$111.3761	$111.38	$111.40	$111.40
Purchase #5	$110.70	3.407%	$114.4715	$114.47	$114.45	$114.50
Purchase #6	$190.51	6.493%	$202.8798	$202.88	$202.90	$202.90
Purchase #7	$213.78	11.718%	$238.8307	$238.83	$238.85	$238.80
7 purchase totals =	$810.10		$874.1101	$874.11	$874.15	$874.10