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	$152.46	7.661%	$164.14	$164.14	$164.15	$164.10
Purchase #2	$241.49	7.620%	$259.8915	$259.89	$259.90	$259.90
Purchase #3	$193.94	13.314%	$219.7612	$219.76	$219.75	$219.80
Purchase #4	$164.61	10.225%	$181.4414	$181.44	$181.45	$181.40
Purchase #5	$66.92	6.787%	$71.4619	$71.46	$71.45	$71.50
Purchase #6	$39.30	5.292%	$41.3798	$41.38	$41.40	$41.40
Purchase #7	$190.81	10.450%	$210.7496	$210.75	$210.75	$210.70
7 purchase totals =	$1,049.53		$1,148.8254	$1,148.82	$1,148.85	$1,148.80