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	$179.85	11.507%	$200.5453	$200.55	$200.55	$200.50
Purchase #2	$229.73	7.418%	$246.7714	$246.77	$246.75	$246.80
Purchase #3	$54.54	12.481%	$61.3471	$61.35	$61.35	$61.30
Purchase #4	$7.69	6.743%	$8.2085	$8.21	$8.20	$8.20
Purchase #5	$224.65	4.341%	$234.4021	$234.40	$234.40	$234.40
Purchase #6	$77.69	3.566%	$80.4604	$80.46	$80.45	$80.50
Purchase #7	$227.75	9.600%	$249.614	$249.61	$249.60	$249.60
7 purchase totals =	$1,001.90		$1,081.3488	$1,081.35	$1,081.30	$1,081.30