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	$118.28	13.541%	$134.2963	$134.30	$134.30	$134.30
Purchase #2	$82.82	8.501%	$89.8605	$89.86	$89.85	$89.90
Purchase #3	$215.35	3.801%	$223.5355	$223.54	$223.55	$223.50
Purchase #4	$117.92	5.810%	$124.7712	$124.77	$124.75	$124.80
Purchase #5	$197.36	3.413%	$204.0959	$204.10	$204.10	$204.10
Purchase #6	$22.93	12.330%	$25.7573	$25.76	$25.75	$25.80
Purchase #7	$205.93	8.417%	$223.2631	$223.26	$223.25	$223.30
7 purchase totals =	$960.59		$1,025.5798	$1,025.59	$1,025.55	$1,025.70