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	$131.67	10.507%	$145.5046	$145.50	$145.50	$145.50
Purchase #2	$199.48	8.360%	$216.1565	$216.16	$216.15	$216.20
Purchase #3	$162.84	5.516%	$171.8223	$171.82	$171.80	$171.80
Purchase #4	$128.61	6.720%	$137.2526	$137.25	$137.25	$137.30
Purchase #5	$216.60	7.612%	$233.0876	$233.09	$233.10	$233.10
Purchase #6	$186.59	6.150%	$198.0653	$198.07	$198.05	$198.10
Purchase #7	$65.62	10.416%	$72.455	$72.46	$72.45	$72.50
7 purchase totals =	$1,091.41		$1,174.3439	$1,174.35	$1,174.30	$1,174.50