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	$69.78	3.342%	$72.112	$72.11	$72.10	$72.10
Purchase #2	$62.85	7.515%	$67.5732	$67.57	$67.55	$67.60
Purchase #3	$201.81	7.701%	$217.3514	$217.35	$217.35	$217.40
Purchase #4	$181.84	4.553%	$190.1192	$190.12	$190.10	$190.10
Purchase #5	$233.75	4.449%	$244.1495	$244.15	$244.15	$244.10
Purchase #6	$149.35	8.789%	$162.4764	$162.48	$162.50	$162.50
Purchase #7	$116.71	5.238%	$122.8233	$122.82	$122.80	$122.80
7 purchase totals =	$1,016.09		$1,076.6050	$1,076.60	$1,076.55	$1,076.60