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	$111.30	11.263%	$123.8357	$123.84	$123.85	$123.80
Purchase #2	$75.39	11.798%	$84.2845	$84.28	$84.30	$84.30
Purchase #3	$142.85	9.632%	$156.6093	$156.61	$156.60	$156.60
Purchase #4	$239.69	5.566%	$253.0311	$253.03	$253.05	$253.00
Purchase #5	$89.87	10.466%	$99.2758	$99.28	$99.30	$99.30
Purchase #6	$88.62	5.824%	$93.7812	$93.78	$93.80	$93.80
Purchase #7	$202.75	8.342%	$219.6634	$219.66	$219.65	$219.70
7 purchase totals =	$950.47		$1,030.4810	$1,030.48	$1,030.55	$1,030.50