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	$185.32	9.567%	$203.0496	$203.05	$203.05	$203.00
Purchase #2	$142.98	7.855%	$154.2111	$154.21	$154.20	$154.20
Purchase #3	$156.84	7.199%	$168.1309	$168.13	$168.15	$168.10
Purchase #4	$177.48	6.551%	$189.1067	$189.11	$189.10	$189.10
Purchase #5	$65.32	8.394%	$70.803	$70.80	$70.80	$70.80
Purchase #6	$116.81	9.397%	$127.7866	$127.79	$127.80	$127.80
Purchase #7	$91.83	12.700%	$103.4924	$103.49	$103.50	$103.50
7 purchase totals =	$936.58		$1,016.5803	$1,016.58	$1,016.60	$1,016.50