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	$166.96	4.419%	$174.338	$174.34	$174.35	$174.30
Purchase #2	$64.53	4.760%	$67.6016	$67.60	$67.60	$67.60
Purchase #3	$203.41	7.454%	$218.5722	$218.57	$218.55	$218.60
Purchase #4	$192.88	3.771%	$200.1535	$200.15	$200.15	$200.20
Purchase #5	$71.76	11.493%	$80.0074	$80.01	$80.00	$80.00
Purchase #6	$109.83	13.503%	$124.6603	$124.66	$124.65	$124.70
Purchase #7	$243.40	12.619%	$274.1146	$274.11	$274.10	$274.10
7 purchase totals =	$1,052.77		$1,139.4476	$1,139.44	$1,139.40	$1,139.50