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	$59.95	4.631%	$62.7263	$62.73	$62.75	$62.70
Purchase #2	$54.63	8.318%	$59.1741	$59.17	$59.15	$59.20
Purchase #3	$185.51	12.142%	$208.0346	$208.03	$208.05	$208.00
Purchase #4	$163.61	9.280%	$178.793	$178.79	$178.80	$178.80
Purchase #5	$174.49	6.691%	$186.1651	$186.17	$186.15	$186.20
Purchase #6	$108.70	6.772%	$116.0612	$116.06	$116.05	$116.10
Purchase #7	$183.97	4.836%	$192.8668	$192.87	$192.85	$192.90
7 purchase totals =	$930.86		$1,003.8211	$1,003.82	$1,003.80	$1,003.90