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	$170.71	11.307%	$190.0122	$190.01	$190.00	$190.00
Purchase #2	$90.87	12.156%	$101.9162	$101.92	$101.90	$101.90
Purchase #3	$37.31	9.163%	$40.7287	$40.73	$40.75	$40.70
Purchase #4	$240.69	5.435%	$253.7715	$253.77	$253.75	$253.80
Purchase #5	$249.91	10.623%	$276.4579	$276.46	$276.45	$276.50
Purchase #6	$49.68	4.484%	$51.9077	$51.91	$51.90	$51.90
Purchase #7	$111.40	5.716%	$117.7676	$117.77	$117.75	$117.80
7 purchase totals =	$950.57		$1,032.5618	$1,032.57	$1,032.50	$1,032.60