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	$55.87	11.860%	$62.4962	$62.50	$62.50	$62.50
Purchase #2	$19.74	5.514%	$20.8285	$20.83	$20.85	$20.80
Purchase #3	$185.39	4.689%	$194.0829	$194.08	$194.10	$194.10
Purchase #4	$236.59	11.724%	$264.3278	$264.33	$264.35	$264.30
Purchase #5	$106.75	13.869%	$121.5552	$121.56	$121.55	$121.60
Purchase #6	$223.50	13.849%	$254.4525	$254.45	$254.45	$254.50
Purchase #7	$153.40	9.507%	$167.9837	$167.98	$168.00	$168.00
7 purchase totals =	$981.24		$1,085.7268	$1,085.73	$1,085.80	$1,085.80