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	$198.97	11.710%	$222.2694	$222.27	$222.25	$222.30
Purchase #2	$234.65	9.312%	$256.5006	$256.50	$256.50	$256.50
Purchase #3	$88.65	8.668%	$96.3342	$96.33	$96.35	$96.30
Purchase #4	$215.64	5.685%	$227.8991	$227.90	$227.90	$227.90
Purchase #5	$211.66	4.617%	$221.4323	$221.43	$221.45	$221.40
Purchase #6	$103.64	12.110%	$116.1908	$116.19	$116.20	$116.20
Purchase #7	$75.25	9.113%	$82.1075	$82.11	$82.10	$82.10
7 purchase totals =	$1,128.46		$1,222.7339	$1,222.73	$1,222.75	$1,222.70