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	$76.80	12.528%	$86.4215	$86.42	$86.40	$86.40
Purchase #2	$74.36	6.124%	$78.9138	$78.91	$78.90	$78.90
Purchase #3	$163.95	13.182%	$185.5619	$185.56	$185.55	$185.60
Purchase #4	$134.96	9.701%	$148.0525	$148.05	$148.05	$148.10
Purchase #5	$240.67	5.459%	$253.8082	$253.81	$253.80	$253.80
Purchase #6	$202.27	7.250%	$216.9346	$216.93	$216.95	$216.90
Purchase #7	$47.62	4.806%	$49.9086	$49.91	$49.90	$49.90
7 purchase totals =	$940.63		$1,019.6011	$1,019.59	$1,019.55	$1,019.60