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	$150.55	13.623%	$171.0594	$171.06	$171.05	$171.10
Purchase #2	$143.54	6.500%	$152.8701	$152.87	$152.85	$152.90
Purchase #3	$194.49	10.515%	$214.9406	$214.94	$214.95	$214.90
Purchase #4	$120.83	8.235%	$130.7804	$130.78	$130.80	$130.80
Purchase #5	$139.63	7.472%	$150.0632	$150.06	$150.05	$150.10
Purchase #6	$38.36	12.658%	$43.2156	$43.22	$43.20	$43.20
Purchase #7	$164.42	4.626%	$172.0261	$172.03	$172.05	$172.00
7 purchase totals =	$951.82		$1,034.9554	$1,034.96	$1,034.95	$1,035.00