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	$96.40	13.709%	$109.6155	$109.62	$109.60	$109.60
Purchase #2	$105.69	6.866%	$112.9467	$112.95	$112.95	$112.90
Purchase #3	$229.32	6.537%	$244.3106	$244.31	$244.30	$244.30
Purchase #4	$211.73	5.796%	$224.0019	$224.00	$224.00	$224.00
Purchase #5	$116.70	7.617%	$125.589	$125.59	$125.60	$125.60
Purchase #6	$158.33	4.738%	$165.8317	$165.83	$165.85	$165.80
Purchase #7	$108.71	7.193%	$116.5295	$116.53	$116.55	$116.50
7 purchase totals =	$1,026.88		$1,098.8249	$1,098.83	$1,098.85	$1,098.70