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	$81.61	4.240%	$85.0703	$85.07	$85.05	$85.10
Purchase #2	$169.30	6.410%	$180.1521	$180.15	$180.15	$180.20
Purchase #3	$166.27	7.350%	$178.4908	$178.49	$178.50	$178.50
Purchase #4	$188.95	3.794%	$196.1188	$196.12	$196.10	$196.10
Purchase #5	$203.95	11.483%	$227.3696	$227.37	$227.35	$227.40
Purchase #6	$162.28	13.259%	$183.7967	$183.80	$183.80	$183.80
Purchase #7	$180.42	5.473%	$190.2944	$190.29	$190.30	$190.30
7 purchase totals =	$1,152.78		$1,241.2927	$1,241.29	$1,241.25	$1,241.40