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	$137.50	4.390%	$143.5363	$143.54	$143.55	$143.50
Purchase #2	$27.27	4.329%	$28.4505	$28.45	$28.45	$28.50
Purchase #3	$19.57	11.336%	$21.7885	$21.79	$21.80	$21.80
Purchase #4	$234.35	9.351%	$256.2641	$256.26	$256.25	$256.30
Purchase #5	$233.26	7.165%	$249.9731	$249.97	$249.95	$250.00
Purchase #6	$222.76	5.440%	$234.8781	$234.88	$234.90	$234.90
Purchase #7	$139.58	5.217%	$146.8619	$146.86	$146.85	$146.90
7 purchase totals =	$1,014.29		$1,081.7525	$1,081.75	$1,081.75	$1,081.90