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	$225.40	8.635%	$244.8633	$244.86	$244.85	$244.90
Purchase #2	$158.38	8.302%	$171.5287	$171.53	$171.55	$171.50
Purchase #3	$76.74	11.839%	$85.8252	$85.83	$85.85	$85.80
Purchase #4	$187.52	11.200%	$208.5222	$208.52	$208.50	$208.50
Purchase #5	$151.59	13.613%	$172.2259	$172.23	$172.25	$172.20
Purchase #6	$41.89	7.622%	$45.0829	$45.08	$45.10	$45.10
Purchase #7	$131.52	10.787%	$145.7071	$145.71	$145.70	$145.70
7 purchase totals =	$973.04		$1,073.7553	$1,073.76	$1,073.80	$1,073.70