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	$153.92	6.683%	$164.2065	$164.21	$164.20	$164.20
Purchase #2	$131.59	7.801%	$141.8553	$141.86	$141.85	$141.90
Purchase #3	$65.50	8.443%	$71.0302	$71.03	$71.05	$71.00
Purchase #4	$47.60	5.150%	$50.0514	$50.05	$50.05	$50.10
Purchase #5	$62.35	4.647%	$65.2474	$65.25	$65.25	$65.20
Purchase #6	$249.80	10.343%	$275.6368	$275.64	$275.65	$275.60
Purchase #7	$216.43	10.566%	$239.298	$239.30	$239.30	$239.30
7 purchase totals =	$927.19		$1,007.3256	$1,007.34	$1,007.35	$1,007.30