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	$103.93	11.114%	$115.4808	$115.48	$115.50	$115.50
Purchase #2	$61.91	9.560%	$67.8286	$67.83	$67.85	$67.80
Purchase #3	$66.78	5.359%	$70.3587	$70.36	$70.35	$70.40
Purchase #4	$82.27	10.434%	$90.8541	$90.85	$90.85	$90.90
Purchase #5	$206.38	8.412%	$223.7407	$223.74	$223.75	$223.70
Purchase #6	$178.25	13.132%	$201.6578	$201.66	$201.65	$201.70
Purchase #7	$211.66	9.295%	$231.3338	$231.33	$231.35	$231.30
7 purchase totals =	$911.18		$1,001.2545	$1,001.25	$1,001.30	$1,001.30