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	$162.46	8.820%	$176.789	$176.79	$176.80	$176.80
Purchase #2	$135.75	10.619%	$150.1653	$150.17	$150.15	$150.20
Purchase #3	$180.47	8.772%	$196.3008	$196.30	$196.30	$196.30
Purchase #4	$5.78	8.425%	$6.267	$6.27	$6.25	$6.30
Purchase #5	$191.55	12.803%	$216.0741	$216.07	$216.05	$216.10
Purchase #6	$238.34	10.692%	$263.8233	$263.82	$263.80	$263.80
Purchase #7	$6.59	9.252%	$7.1997	$7.20	$7.20	$7.20
7 purchase totals =	$920.94		$1,016.6192	$1,016.62	$1,016.55	$1,016.70