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	$144.51	10.813%	$160.1359	$160.14	$160.15	$160.10
Purchase #2	$98.78	4.822%	$103.5432	$103.54	$103.55	$103.50
Purchase #3	$241.82	11.514%	$269.6632	$269.66	$269.65	$269.70
Purchase #4	$171.69	8.129%	$185.6467	$185.65	$185.65	$185.60
Purchase #5	$162.46	11.305%	$180.8261	$180.83	$180.85	$180.80
Purchase #6	$147.37	12.315%	$165.5186	$165.52	$165.50	$165.50
Purchase #7	$46.40	8.349%	$50.2739	$50.27	$50.25	$50.30
7 purchase totals =	$1,013.03		$1,115.6076	$1,115.61	$1,115.60	$1,115.50