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	$161.25	7.216%	$172.8858	$172.89	$172.90	$172.90
Purchase #2	$68.75	12.288%	$77.198	$77.20	$77.20	$77.20
Purchase #3	$215.92	6.556%	$230.0757	$230.08	$230.10	$230.10
Purchase #4	$190.81	10.819%	$211.4537	$211.45	$211.45	$211.50
Purchase #5	$190.38	9.462%	$208.3938	$208.39	$208.40	$208.40
Purchase #6	$27.32	3.850%	$28.3718	$28.37	$28.35	$28.40
Purchase #7	$99.32	6.130%	$105.4083	$105.41	$105.40	$105.40
7 purchase totals =	$953.75		$1,033.7871	$1,033.79	$1,033.80	$1,033.90