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	$37.43	9.691%	$41.0573	$41.06	$41.05	$41.10
Purchase #2	$245.94	4.124%	$256.0826	$256.08	$256.10	$256.10
Purchase #3	$163.91	4.483%	$171.2581	$171.26	$171.25	$171.30
Purchase #4	$168.77	13.201%	$191.0493	$191.05	$191.05	$191.00
Purchase #5	$171.81	10.467%	$189.7934	$189.79	$189.80	$189.80
Purchase #6	$107.69	3.276%	$111.2179	$111.22	$111.20	$111.20
Purchase #7	$92.88	13.307%	$105.2395	$105.24	$105.25	$105.20
7 purchase totals =	$988.43		$1,065.6981	$1,065.70	$1,065.70	$1,065.70