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	$199.26	6.821%	$212.8515	$212.85	$212.85	$212.90
Purchase #2	$162.66	6.174%	$172.7026	$172.70	$172.70	$172.70
Purchase #3	$174.99	7.834%	$188.6987	$188.70	$188.70	$188.70
Purchase #4	$171.48	9.840%	$188.3536	$188.35	$188.35	$188.40
Purchase #5	$101.96	9.403%	$111.5473	$111.55	$111.55	$111.50
Purchase #6	$158.35	4.828%	$165.9951	$166.00	$166.00	$166.00
Purchase #7	$86.70	3.299%	$89.5602	$89.56	$89.55	$89.60
7 purchase totals =	$1,055.40		$1,129.7090	$1,129.71	$1,129.70	$1,129.80