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	$38.52	8.484%	$41.788	$41.79	$41.80	$41.80
Purchase #2	$193.88	3.250%	$200.1811	$200.18	$200.20	$200.20
Purchase #3	$229.91	9.574%	$251.9216	$251.92	$251.90	$251.90
Purchase #4	$47.51	6.273%	$50.4903	$50.49	$50.50	$50.50
Purchase #5	$173.59	13.365%	$196.7903	$196.79	$196.80	$196.80
Purchase #6	$195.73	9.636%	$214.5905	$214.59	$214.60	$214.60
Purchase #7	$166.52	13.702%	$189.3366	$189.34	$189.35	$189.30
7 purchase totals =	$1,045.66		$1,145.0984	$1,145.10	$1,145.15	$1,145.10