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	$203.75	7.581%	$219.1963	$219.20	$219.20	$219.20
Purchase #2	$164.90	12.406%	$185.3575	$185.36	$185.35	$185.40
Purchase #3	$17.76	13.326%	$20.1267	$20.13	$20.15	$20.10
Purchase #4	$247.48	13.392%	$280.6225	$280.62	$280.60	$280.60
Purchase #5	$145.90	3.607%	$151.1626	$151.16	$151.15	$151.20
Purchase #6	$78.82	3.155%	$81.3068	$81.31	$81.30	$81.30
Purchase #7	$109.51	3.369%	$113.1994	$113.20	$113.20	$113.20
7 purchase totals =	$968.12		$1,050.9718	$1,050.98	$1,050.95	$1,051.00