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	$218.87	4.464%	$228.6404	$228.64	$228.65	$228.60
Purchase #2	$60.46	8.734%	$65.7406	$65.74	$65.75	$65.70
Purchase #3	$153.78	13.357%	$174.3204	$174.32	$174.30	$174.30
Purchase #4	$172.62	13.839%	$196.5089	$196.51	$196.50	$196.50
Purchase #5	$128.26	8.811%	$139.561	$139.56	$139.55	$139.60
Purchase #6	$126.98	7.581%	$136.6064	$136.61	$136.60	$136.60
Purchase #7	$238.54	11.299%	$265.4926	$265.49	$265.50	$265.50
7 purchase totals =	$1,099.51		$1,206.8703	$1,206.87	$1,206.85	$1,206.80