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	$86.48	3.783%	$89.7515	$89.75	$89.75	$89.80
Purchase #2	$166.82	9.204%	$182.1741	$182.17	$182.15	$182.20
Purchase #3	$25.39	13.702%	$28.8689	$28.87	$28.85	$28.90
Purchase #4	$244.83	13.153%	$277.0325	$277.03	$277.05	$277.00
Purchase #5	$173.48	4.344%	$181.016	$181.02	$181.00	$181.00
Purchase #6	$83.78	7.192%	$89.8055	$89.81	$89.80	$89.80
Purchase #7	$169.57	9.306%	$185.3502	$185.35	$185.35	$185.40
7 purchase totals =	$950.35		$1,033.9987	$1,034.00	$1,033.95	$1,034.10