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	$232.45	9.859%	$255.3672	$255.37	$255.35	$255.40
Purchase #2	$120.35	6.828%	$128.5675	$128.57	$128.55	$128.60
Purchase #3	$54.57	8.798%	$59.3711	$59.37	$59.35	$59.40
Purchase #4	$235.59	6.813%	$251.6407	$251.64	$251.65	$251.60
Purchase #5	$17.36	6.605%	$18.5066	$18.51	$18.50	$18.50
Purchase #6	$216.88	6.650%	$231.3025	$231.30	$231.30	$231.30
Purchase #7	$226.53	8.785%	$246.4307	$246.43	$246.45	$246.40
7 purchase totals =	$1,103.73		$1,191.1863	$1,191.19	$1,191.15	$1,191.20