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	$70.76	8.605%	$76.8489	$76.85	$76.85	$76.80
Purchase #2	$107.77	9.224%	$117.7107	$117.71	$117.70	$117.70
Purchase #3	$78.86	4.413%	$82.3401	$82.34	$82.35	$82.30
Purchase #4	$115.47	9.605%	$126.5609	$126.56	$126.55	$126.60
Purchase #5	$158.38	4.616%	$165.6908	$165.69	$165.70	$165.70
Purchase #6	$198.91	7.410%	$213.6492	$213.65	$213.65	$213.60
Purchase #7	$75.68	3.217%	$78.1146	$78.11	$78.10	$78.10
7 purchase totals =	$805.83		$860.9152	$860.91	$860.90	$860.80