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	$249.36	3.114%	$257.1251	$257.13	$257.15	$257.10
Purchase #2	$81.95	3.824%	$85.0838	$85.08	$85.10	$85.10
Purchase #3	$80.79	5.663%	$85.3651	$85.37	$85.35	$85.40
Purchase #4	$192.90	8.804%	$209.8829	$209.88	$209.90	$209.90
Purchase #5	$173.70	13.346%	$196.882	$196.88	$196.90	$196.90
Purchase #6	$41.79	11.447%	$46.5737	$46.57	$46.55	$46.60
Purchase #7	$225.81	3.188%	$233.0088	$233.01	$233.00	$233.00
7 purchase totals =	$1,046.30		$1,113.9214	$1,113.92	$1,113.95	$1,114.00