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	$72.64	9.478%	$79.5248	$79.52	$79.50	$79.50
Purchase #2	$6.34	9.273%	$6.9279	$6.93	$6.95	$6.90
Purchase #3	$187.78	11.338%	$209.0705	$209.07	$209.05	$209.10
Purchase #4	$155.99	11.847%	$174.4701	$174.47	$174.45	$174.50
Purchase #5	$240.46	9.579%	$263.4937	$263.49	$263.50	$263.50
Purchase #6	$119.72	7.516%	$128.7182	$128.72	$128.70	$128.70
Purchase #7	$141.85	5.873%	$150.1809	$150.18	$150.20	$150.20
7 purchase totals =	$924.78		$1,012.3861	$1,012.38	$1,012.35	$1,012.40