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	$158.59	3.654%	$164.3849	$164.38	$164.40	$164.40
Purchase #2	$37.99	10.754%	$42.0754	$42.08	$42.10	$42.10
Purchase #3	$87.44	4.570%	$91.436	$91.44	$91.45	$91.40
Purchase #4	$242.43	6.536%	$258.2752	$258.28	$258.30	$258.30
Purchase #5	$73.43	6.334%	$78.0811	$78.08	$78.10	$78.10
Purchase #6	$239.32	11.838%	$267.6507	$267.65	$267.65	$267.70
Purchase #7	$172.67	11.838%	$193.1107	$193.11	$193.10	$193.10
7 purchase totals =	$1,011.87		$1,095.0140	$1,095.02	$1,095.10	$1,095.10