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	$215.57	3.476%	$223.0632	$223.06	$223.05	$223.10
Purchase #2	$91.85	3.845%	$95.3816	$95.38	$95.40	$95.40
Purchase #3	$158.51	11.117%	$176.1316	$176.13	$176.15	$176.10
Purchase #4	$53.25	11.832%	$59.5505	$59.55	$59.55	$59.60
Purchase #5	$128.65	4.178%	$134.025	$134.03	$134.05	$134.00
Purchase #6	$86.25	13.500%	$97.8938	$97.89	$97.90	$97.90
Purchase #7	$230.30	6.731%	$245.8015	$245.80	$245.80	$245.80
7 purchase totals =	$964.38		$1,031.8472	$1,031.84	$1,031.90	$1,031.90