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	$216.64	7.694%	$233.3083	$233.31	$233.30	$233.30
Purchase #2	$169.47	12.183%	$190.1165	$190.12	$190.10	$190.10
Purchase #3	$79.91	3.339%	$82.5782	$82.58	$82.60	$82.60
Purchase #4	$96.39	9.356%	$105.4082	$105.41	$105.40	$105.40
Purchase #5	$205.59	3.726%	$213.2503	$213.25	$213.25	$213.30
Purchase #6	$181.96	4.816%	$190.7232	$190.72	$190.70	$190.70
Purchase #7	$210.72	5.278%	$221.8418	$221.84	$221.85	$221.80
7 purchase totals =	$1,160.68		$1,237.2265	$1,237.23	$1,237.20	$1,237.20