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	$65.73	10.382%	$72.5541	$72.55	$72.55	$72.60
Purchase #2	$55.42	9.103%	$60.4649	$60.46	$60.45	$60.50
Purchase #3	$33.94	6.380%	$36.1054	$36.11	$36.10	$36.10
Purchase #4	$38.91	11.442%	$43.3621	$43.36	$43.35	$43.40
Purchase #5	$89.47	7.665%	$96.3279	$96.33	$96.35	$96.30
Purchase #6	$162.91	6.645%	$173.7354	$173.74	$173.75	$173.70
Purchase #7	$71.70	7.454%	$77.0445	$77.04	$77.05	$77.00
7 purchase totals =	$518.08		$559.5943	$559.59	$559.60	$559.60