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	$51.74	10.819%	$57.3378	$57.34	$57.35	$57.30
Purchase #2	$16.44	12.214%	$18.448	$18.45	$18.45	$18.40
Purchase #3	$84.51	7.424%	$90.784	$90.78	$90.80	$90.80
Purchase #4	$174.36	7.786%	$187.9357	$187.94	$187.95	$187.90
Purchase #5	$160.64	3.264%	$165.8833	$165.88	$165.90	$165.90
Purchase #6	$14.63	8.297%	$15.8439	$15.84	$15.85	$15.80
Purchase #7	$79.80	12.556%	$89.8197	$89.82	$89.80	$89.80
7 purchase totals =	$582.12		$626.0524	$626.05	$626.10	$625.90