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	$98.80	7.444%	$106.1547	$106.15	$106.15	$106.20
Purchase #2	$249.38	7.201%	$267.3379	$267.34	$267.35	$267.30
Purchase #3	$195.30	9.191%	$213.25	$213.25	$213.25	$213.30
Purchase #4	$77.53	5.544%	$81.8283	$81.83	$81.85	$81.80
Purchase #5	$92.50	13.328%	$104.8284	$104.83	$104.85	$104.80
Purchase #6	$155.53	5.819%	$164.5803	$164.58	$164.60	$164.60
Purchase #7	$119.47	7.569%	$128.5127	$128.51	$128.50	$128.50
7 purchase totals =	$988.51		$1,066.4923	$1,066.49	$1,066.55	$1,066.50