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	$191.91	5.196%	$201.8816	$201.88	$201.90	$201.90
Purchase #2	$31.98	4.486%	$33.4146	$33.41	$33.40	$33.40
Purchase #3	$37.83	12.238%	$42.4596	$42.46	$42.45	$42.50
Purchase #4	$29.54	8.138%	$31.944	$31.94	$31.95	$31.90
Purchase #5	$74.64	3.630%	$77.3494	$77.35	$77.35	$77.30
Purchase #6	$196.25	5.566%	$207.1733	$207.17	$207.15	$207.20
Purchase #7	$114.94	11.300%	$127.9282	$127.93	$127.95	$127.90
7 purchase totals =	$677.09		$722.1507	$722.14	$722.15	$722.10