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	$203.33	3.526%	$210.4994	$210.50	$210.50	$210.50
Purchase #2	$127.68	11.865%	$142.8292	$142.83	$142.85	$142.80
Purchase #3	$174.61	12.508%	$196.4502	$196.45	$196.45	$196.50
Purchase #4	$213.68	8.540%	$231.9283	$231.93	$231.95	$231.90
Purchase #5	$125.28	13.827%	$142.6025	$142.60	$142.60	$142.60
Purchase #6	$152.98	11.404%	$170.4258	$170.43	$170.45	$170.40
Purchase #7	$8.30	4.579%	$8.6801	$8.68	$8.70	$8.70
7 purchase totals =	$1,005.86		$1,103.4155	$1,103.42	$1,103.50	$1,103.40