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	$211.86	5.498%	$223.5081	$223.51	$223.50	$223.50
Purchase #2	$25.80	7.200%	$27.6576	$27.66	$27.65	$27.70
Purchase #3	$199.78	12.263%	$224.279	$224.28	$224.30	$224.30
Purchase #4	$94.75	11.366%	$105.5193	$105.52	$105.50	$105.50
Purchase #5	$175.39	12.233%	$196.8455	$196.85	$196.85	$196.80
Purchase #6	$103.82	4.412%	$108.4005	$108.40	$108.40	$108.40
Purchase #7	$172.71	7.865%	$186.2936	$186.29	$186.30	$186.30
7 purchase totals =	$984.11		$1,072.5036	$1,072.51	$1,072.50	$1,072.50