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	$170.68	7.140%	$182.8666	$182.87	$182.85	$182.90
Purchase #2	$193.33	3.696%	$200.4755	$200.48	$200.50	$200.50
Purchase #3	$105.65	6.573%	$112.5944	$112.59	$112.60	$112.60
Purchase #4	$238.91	5.371%	$251.7419	$251.74	$251.75	$251.70
Purchase #5	$102.76	9.411%	$112.4307	$112.43	$112.45	$112.40
Purchase #6	$114.39	3.872%	$118.8192	$118.82	$118.80	$118.80
Purchase #7	$30.93	13.603%	$35.1374	$35.14	$35.15	$35.10
7 purchase totals =	$956.65		$1,014.0657	$1,014.07	$1,014.10	$1,014.00