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	$225.98	12.165%	$253.4705	$253.47	$253.45	$253.50
Purchase #2	$101.81	3.296%	$105.1657	$105.17	$105.15	$105.20
Purchase #3	$179.68	9.226%	$196.2573	$196.26	$196.25	$196.30
Purchase #4	$29.83	13.313%	$33.8013	$33.80	$33.80	$33.80
Purchase #5	$214.70	9.369%	$234.8152	$234.82	$234.80	$234.80
Purchase #6	$24.27	13.311%	$27.5006	$27.50	$27.50	$27.50
Purchase #7	$154.83	7.304%	$166.1388	$166.14	$166.15	$166.10
7 purchase totals =	$931.10		$1,017.1494	$1,017.16	$1,017.10	$1,017.20