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	$68.85	4.458%	$71.9193	$71.92	$71.90	$71.90
Purchase #2	$230.75	5.349%	$243.0928	$243.09	$243.10	$243.10
Purchase #3	$80.82	10.540%	$89.3384	$89.34	$89.35	$89.30
Purchase #4	$64.47	9.790%	$70.7816	$70.78	$70.80	$70.80
Purchase #5	$74.76	4.113%	$77.8349	$77.83	$77.85	$77.80
Purchase #6	$222.31	5.140%	$233.7367	$233.74	$233.75	$233.70
Purchase #7	$250.96	10.820%	$278.1139	$278.11	$278.10	$278.10
7 purchase totals =	$992.92		$1,064.8176	$1,064.81	$1,064.85	$1,064.70