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	$106.84	5.593%	$112.8156	$112.82	$112.80	$112.80
Purchase #2	$177.49	6.121%	$188.3542	$188.35	$188.35	$188.40
Purchase #3	$153.88	9.308%	$168.2032	$168.20	$168.20	$168.20
Purchase #4	$48.40	13.257%	$54.8164	$54.82	$54.80	$54.80
Purchase #5	$148.91	13.607%	$169.1722	$169.17	$169.15	$169.20
Purchase #6	$45.55	11.463%	$50.7714	$50.77	$50.75	$50.80
Purchase #7	$245.38	7.502%	$263.7884	$263.79	$263.80	$263.80
7 purchase totals =	$926.45		$1,007.9214	$1,007.92	$1,007.85	$1,008.00