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	$112.40	10.266%	$123.939	$123.94	$123.95	$123.90
Purchase #2	$29.57	6.637%	$31.5326	$31.53	$31.55	$31.50
Purchase #3	$97.98	7.253%	$105.0865	$105.09	$105.10	$105.10
Purchase #4	$159.99	10.177%	$176.2722	$176.27	$176.25	$176.30
Purchase #5	$79.35	3.583%	$82.1931	$82.19	$82.20	$82.20
Purchase #6	$229.82	7.676%	$247.461	$247.46	$247.45	$247.50
Purchase #7	$101.33	8.373%	$109.8144	$109.81	$109.80	$109.80
7 purchase totals =	$810.44		$876.2988	$876.29	$876.30	$876.30