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	$121.69	3.140%	$125.5111	$125.51	$125.50	$125.50
Purchase #2	$47.38	6.167%	$50.3019	$50.30	$50.30	$50.30
Purchase #3	$173.55	13.493%	$196.9671	$196.97	$196.95	$197.00
Purchase #4	$73.31	4.529%	$76.6302	$76.63	$76.65	$76.60
Purchase #5	$169.37	9.612%	$185.6498	$185.65	$185.65	$185.60
Purchase #6	$62.88	7.754%	$67.7557	$67.76	$67.75	$67.80
Purchase #7	$78.37	6.173%	$83.2078	$83.21	$83.20	$83.20
7 purchase totals =	$726.55		$786.0236	$786.03	$786.00	$786.00