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	$88.40	7.673%	$95.1829	$95.18	$95.20	$95.20
Purchase #2	$244.72	5.774%	$258.8501	$258.85	$258.85	$258.90
Purchase #3	$203.38	13.809%	$231.4647	$231.46	$231.45	$231.50
Purchase #4	$109.25	6.732%	$116.6047	$116.60	$116.60	$116.60
Purchase #5	$250.41	11.517%	$279.2497	$279.25	$279.25	$279.20
Purchase #6	$98.62	6.450%	$104.981	$104.98	$105.00	$105.00
Purchase #7	$39.70	10.601%	$43.9086	$43.91	$43.90	$43.90
7 purchase totals =	$1,034.48		$1,130.2417	$1,130.23	$1,130.25	$1,130.30