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	$249.25	10.163%	$274.5813	$274.58	$274.60	$274.60
Purchase #2	$114.41	3.284%	$118.1672	$118.17	$118.15	$118.20
Purchase #3	$56.65	5.589%	$59.8162	$59.82	$59.80	$59.80
Purchase #4	$180.35	10.573%	$199.4184	$199.42	$199.40	$199.40
Purchase #5	$143.50	9.487%	$157.1138	$157.11	$157.10	$157.10
Purchase #6	$57.53	3.185%	$59.3623	$59.36	$59.35	$59.40
Purchase #7	$250.48	11.699%	$279.7837	$279.78	$279.80	$279.80
7 purchase totals =	$1,052.17		$1,148.2429	$1,148.24	$1,148.20	$1,148.30