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	$179.61	3.800%	$186.4352	$186.44	$186.45	$186.40
Purchase #2	$198.46	7.237%	$212.8226	$212.82	$212.80	$212.80
Purchase #3	$69.85	12.570%	$78.6301	$78.63	$78.65	$78.60
Purchase #4	$132.32	12.274%	$148.561	$148.56	$148.55	$148.60
Purchase #5	$94.51	8.804%	$102.8307	$102.83	$102.85	$102.80
Purchase #6	$238.86	6.767%	$255.0237	$255.02	$255.00	$255.00
Purchase #7	$115.34	9.118%	$125.8567	$125.86	$125.85	$125.90
7 purchase totals =	$1,028.95		$1,110.1600	$1,110.16	$1,110.15	$1,110.10