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	$166.98	7.415%	$179.3616	$179.36	$179.35	$179.40
Purchase #2	$63.73	6.373%	$67.7915	$67.79	$67.80	$67.80
Purchase #3	$117.77	11.582%	$131.4101	$131.41	$131.40	$131.40
Purchase #4	$105.78	10.532%	$116.9207	$116.92	$116.90	$116.90
Purchase #5	$243.36	13.805%	$276.9558	$276.96	$276.95	$277.00
Purchase #6	$110.78	4.790%	$116.0864	$116.09	$116.10	$116.10
Purchase #7	$133.41	5.182%	$140.3233	$140.32	$140.30	$140.30
7 purchase totals =	$941.81		$1,028.8494	$1,028.85	$1,028.80	$1,028.90