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	$207.31	6.410%	$220.5986	$220.60	$220.60	$220.60
Purchase #2	$119.51	11.604%	$133.3779	$133.38	$133.40	$133.40
Purchase #3	$40.77	12.296%	$45.7831	$45.78	$45.80	$45.80
Purchase #4	$153.58	7.499%	$165.097	$165.10	$165.10	$165.10
Purchase #5	$134.38	6.182%	$142.6874	$142.69	$142.70	$142.70
Purchase #6	$246.91	7.785%	$266.1319	$266.13	$266.15	$266.10
Purchase #7	$155.86	7.527%	$167.5916	$167.59	$167.60	$167.60
7 purchase totals =	$1,058.32		$1,141.2675	$1,141.27	$1,141.35	$1,141.30