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	$40.90	10.279%	$45.1041	$45.10	$45.10	$45.10
Purchase #2	$180.71	11.381%	$201.2766	$201.28	$201.30	$201.30
Purchase #3	$59.52	9.357%	$65.0893	$65.09	$65.10	$65.10
Purchase #4	$85.62	9.148%	$93.4525	$93.45	$93.45	$93.50
Purchase #5	$166.93	8.381%	$180.9204	$180.92	$180.90	$180.90
Purchase #6	$111.60	10.537%	$123.3593	$123.36	$123.35	$123.40
Purchase #7	$67.49	6.273%	$71.7236	$71.72	$71.70	$71.70
7 purchase totals =	$712.77		$780.9258	$780.92	$780.90	$781.00