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	$160.83	11.833%	$179.861	$179.86	$179.85	$179.90
Purchase #2	$148.39	4.623%	$155.2501	$155.25	$155.25	$155.30
Purchase #3	$179.41	7.132%	$192.2055	$192.21	$192.20	$192.20
Purchase #4	$88.59	6.172%	$94.0578	$94.06	$94.05	$94.10
Purchase #5	$130.85	11.431%	$145.8075	$145.81	$145.80	$145.80
Purchase #6	$53.69	4.652%	$56.1877	$56.19	$56.20	$56.20
Purchase #7	$176.74	7.459%	$189.923	$189.92	$189.90	$189.90
7 purchase totals =	$938.50		$1,013.2926	$1,013.30	$1,013.25	$1,013.40