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	$57.47	6.654%	$61.2941	$61.29	$61.30	$61.30
Purchase #2	$38.33	7.367%	$41.1538	$41.15	$41.15	$41.20
Purchase #3	$41.32	3.619%	$42.8154	$42.82	$42.80	$42.80
Purchase #4	$133.54	7.240%	$143.2083	$143.21	$143.20	$143.20
Purchase #5	$45.94	9.819%	$50.4508	$50.45	$50.45	$50.50
Purchase #6	$162.40	7.639%	$174.8057	$174.81	$174.80	$174.80
Purchase #7	$224.42	5.374%	$236.4803	$236.48	$236.50	$236.50
7 purchase totals =	$703.42		$750.2084	$750.21	$750.20	$750.30