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	$164.42	4.570%	$171.934	$171.93	$171.95	$171.90
Purchase #2	$49.80	8.440%	$54.0031	$54.00	$54.00	$54.00
Purchase #3	$165.77	11.816%	$185.3574	$185.36	$185.35	$185.40
Purchase #4	$163.58	13.349%	$185.4163	$185.42	$185.40	$185.40
Purchase #5	$106.97	7.755%	$115.2655	$115.27	$115.25	$115.30
Purchase #6	$171.52	9.475%	$187.7715	$187.77	$187.75	$187.80
Purchase #7	$185.98	5.593%	$196.3819	$196.38	$196.40	$196.40
7 purchase totals =	$1,008.04		$1,096.1297	$1,096.13	$1,096.10	$1,096.20