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	$31.77	7.451%	$34.1372	$34.14	$34.15	$34.10
Purchase #2	$110.92	3.220%	$114.4916	$114.49	$114.50	$114.50
Purchase #3	$191.79	3.848%	$199.1701	$199.17	$199.15	$199.20
Purchase #4	$39.78	9.236%	$43.4541	$43.45	$43.45	$43.50
Purchase #5	$149.89	3.746%	$155.5049	$155.50	$155.50	$155.50
Purchase #6	$207.56	6.492%	$221.0348	$221.03	$221.05	$221.00
Purchase #7	$213.44	13.155%	$241.518	$241.52	$241.50	$241.50
7 purchase totals =	$945.15		$1,009.3107	$1,009.30	$1,009.30	$1,009.30