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	$102.26	5.166%	$107.5428	$107.54	$107.55	$107.50
Purchase #2	$87.42	8.644%	$94.9766	$94.98	$95.00	$95.00
Purchase #3	$156.50	6.419%	$166.5457	$166.55	$166.55	$166.50
Purchase #4	$147.86	11.323%	$164.6022	$164.60	$164.60	$164.60
Purchase #5	$49.29	7.728%	$53.0991	$53.10	$53.10	$53.10
Purchase #6	$213.56	11.213%	$237.5065	$237.51	$237.50	$237.50
Purchase #7	$171.72	11.441%	$191.3665	$191.37	$191.35	$191.40
7 purchase totals =	$928.61		$1,015.6394	$1,015.65	$1,015.65	$1,015.60