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	$206.84	3.816%	$214.733	$214.73	$214.75	$214.70
Purchase #2	$117.66	11.404%	$131.0779	$131.08	$131.10	$131.10
Purchase #3	$183.90	6.670%	$196.1661	$196.17	$196.15	$196.20
Purchase #4	$29.81	9.405%	$32.6136	$32.61	$32.60	$32.60
Purchase #5	$71.54	11.718%	$79.9231	$79.92	$79.90	$79.90
Purchase #6	$111.37	6.127%	$118.1936	$118.19	$118.20	$118.20
Purchase #7	$27.75	10.306%	$30.6099	$30.61	$30.60	$30.60
7 purchase totals =	$748.87		$803.3172	$803.31	$803.30	$803.30