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	$171.34	12.783%	$193.2424	$193.24	$193.25	$193.20
Purchase #2	$100.58	10.769%	$111.4115	$111.41	$111.40	$111.40
Purchase #3	$63.35	6.601%	$67.5317	$67.53	$67.55	$67.50
Purchase #4	$212.30	12.370%	$238.5615	$238.56	$238.55	$238.60
Purchase #5	$35.92	11.801%	$40.1589	$40.16	$40.15	$40.20
Purchase #6	$96.98	12.269%	$108.8785	$108.88	$108.90	$108.90
Purchase #7	$50.90	3.401%	$52.6311	$52.63	$52.65	$52.60
7 purchase totals =	$731.37		$812.4156	$812.41	$812.45	$812.40