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	$247.83	6.824%	$264.7419	$264.74	$264.75	$264.70
Purchase #2	$250.90	5.367%	$264.3658	$264.37	$264.35	$264.40
Purchase #3	$234.34	6.592%	$249.7877	$249.79	$249.80	$249.80
Purchase #4	$41.92	7.844%	$45.2082	$45.21	$45.20	$45.20
Purchase #5	$76.59	11.729%	$85.5732	$85.57	$85.55	$85.60
Purchase #6	$218.72	3.158%	$225.6272	$225.63	$225.65	$225.60
Purchase #7	$233.85	10.121%	$257.518	$257.52	$257.50	$257.50
7 purchase totals =	$1,304.15		$1,392.8220	$1,392.83	$1,392.80	$1,392.80