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	$72.39	13.837%	$82.4066	$82.41	$82.40	$82.40
Purchase #2	$20.77	3.452%	$21.487	$21.49	$21.50	$21.50
Purchase #3	$193.80	3.276%	$200.1489	$200.15	$200.15	$200.10
Purchase #4	$229.65	12.481%	$258.3126	$258.31	$258.30	$258.30
Purchase #5	$177.97	8.772%	$193.5815	$193.58	$193.60	$193.60
Purchase #6	$198.59	8.323%	$215.1186	$215.12	$215.10	$215.10
Purchase #7	$80.55	4.236%	$83.9621	$83.96	$83.95	$84.00
7 purchase totals =	$973.72		$1,055.0173	$1,055.02	$1,055.00	$1,055.00