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	$142.29	6.254%	$151.1888	$151.19	$151.20	$151.20
Purchase #2	$200.46	7.326%	$215.1457	$215.15	$215.15	$215.10
Purchase #3	$65.72	8.830%	$71.5231	$71.52	$71.50	$71.50
Purchase #4	$224.81	8.347%	$243.5749	$243.57	$243.55	$243.60
Purchase #5	$54.59	6.802%	$58.3032	$58.30	$58.30	$58.30
Purchase #6	$40.52	10.753%	$44.8771	$44.88	$44.90	$44.90
Purchase #7	$13.67	10.153%	$15.0579	$15.06	$15.05	$15.10
7 purchase totals =	$742.06		$799.6707	$799.67	$799.65	$799.70