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	$200.63	6.207%	$213.0831	$213.08	$213.10	$213.10
Purchase #2	$78.52	13.482%	$89.1061	$89.11	$89.10	$89.10
Purchase #3	$76.55	12.154%	$85.8539	$85.85	$85.85	$85.90
Purchase #4	$186.53	6.695%	$199.0182	$199.02	$199.00	$199.00
Purchase #5	$39.50	6.196%	$41.9474	$41.95	$41.95	$41.90
Purchase #6	$160.64	7.603%	$172.8535	$172.85	$172.85	$172.90
Purchase #7	$213.59	11.133%	$237.369	$237.37	$237.35	$237.40
7 purchase totals =	$955.96		$1,039.2312	$1,039.23	$1,039.20	$1,039.30